U.S. patent application number 13/665442 was filed with the patent office on 2013-05-09 for control apparatus, control method and control system.
This patent application is currently assigned to SONY CORPORATION. The applicant listed for this patent is SONY CORPORATION. Invention is credited to Yoshihito ISHIBASHI, Rui KAMADA, Junichi SAWADA.
Application Number | 20130113437 13/665442 |
Document ID | / |
Family ID | 48207234 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130113437 |
Kind Code |
A1 |
ISHIBASHI; Yoshihito ; et
al. |
May 9, 2013 |
CONTROL APPARATUS, CONTROL METHOD AND CONTROL SYSTEM
Abstract
Disclosed herein is a control apparatus, including: a
discrimination section configured to discriminate a plurality of
battery units which are to share and output electric power required
by a load; and a control section configured to carry out discharge
control for the battery units in response to a situation of each of
batteries which the battery units individually have.
Inventors: |
ISHIBASHI; Yoshihito;
(Tokyo, JP) ; SAWADA; Junichi; (Tokyo, JP)
; KAMADA; Rui; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SONY CORPORATION; |
Tokyo |
|
JP |
|
|
Assignee: |
SONY CORPORATION
Tokyo
JP
|
Family ID: |
48207234 |
Appl. No.: |
13/665442 |
Filed: |
October 31, 2012 |
Current U.S.
Class: |
320/136 |
Current CPC
Class: |
H02J 7/008 20130101;
H02J 7/00 20130101; H02J 2007/0067 20130101; Y02E 10/76 20130101;
H02J 7/35 20130101; H02J 1/108 20130101; H02J 7/0063 20130101; Y02E
10/56 20130101; H02J 2300/28 20200101; G05F 1/67 20130101 |
Class at
Publication: |
320/136 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2011 |
JP |
2011-243964 |
Claims
1. A control apparatus, comprising: a discrimination section
configured to discriminate a plurality of battery units which are
to share and output electric power required by a load; and a
control section configured to carry out discharge control for the
battery units in response to a situation of each of batteries which
the battery units individually have.
2. The control apparatus according to claim 1, wherein the control
section carries out the discharge control by determining a
discharge amount for each of the battery units.
3. The control apparatus according to claim 2, wherein said control
section determines a discharge amount for each of the battery units
by setting a discharge period with respect to a reference
signal.
4. The control apparatus according to claim 3, wherein a discharge
period for which a predetermined one of the battery units is to
carry out the discharge process and a discharge period for which
another one of the battery units is to carry out the discharge
process overlap with each other.
5. The control apparatus according to claim 1, wherein the
situation of each of the batteries is at least one of a remaining
capacity of the battery, a use history of the battery and a
temperature of the battery.
6. The control apparatus according to claim 1, wherein the
discrimination section successively connects the battery units to
the load and monitors a voltage supplied from the connected one of
the battery units to discriminate the battery unit.
7. A control method, comprising: discriminating a plurality of
battery units which are to share and output electric power required
by a load; and carrying out discharge control for the battery units
in response to a situation of each of batteries which the battery
units individually have.
8. A control system, comprising: a plurality of battery units; and
a control apparatus connected to the battery units; the control
apparatus including a discrimination section configured to
discriminate a plurality of battery units which are to share and
output electric power required by a load from among the battery
units, and a control section configured to carry out discharge
control for the battery units in response to a situation of each of
batteries which the battery units individually have.
Description
BACKGROUND
[0001] The present disclosure relates to a control apparatus, a
control method and a control system by which, for example, when
discharge from a plurality of battery units is carried out, the
discharge amount is controlled for each battery unit.
[0002] In recent years, in order to enhance the output capacity, a
plurality of power supply modules are connected in parallel such
that electric power is supplied from the power supply modules. For
example, Japanese Patent Laid-open No. 2006-034047 discloses a
power supply apparatus wherein a plurality of power supply units
are connected in parallel and are successively started up.
SUMMARY
[0003] In the power supply apparatus disclosed in Japanese Patent
Laid-Open No. 2006-034047 mentioned above, all power supply units
are started up finally. Although it is preferable, when a plurality
of power supply units connected in parallel operate, to control
output voltages of the power supply units so as to be equal to each
other with a high degree of accuracy, it is actually difficult to
make the output voltages fully equal to each other. Therefore, only
a battery of that one of the power supply units which outputs the
highest output voltage discharges, and there is a problem that only
a specific battery is exhausted. Also it is another problem that
the discharge amount cannot be controlled for each power supply
unit.
[0004] Therefore, it is desirable to provide a control apparatus, a
control method and a control system by which, for example, when
discharge from a plurality of battery units is carried out, the
discharge amount is controlled for each battery unit.
[0005] According to an embodiment of the present disclosure, there
is provided a control apparatus including a discrimination section
configured to discriminate a plurality of battery units which are
to share and output electric power required by a load, and a
control section configured to carry out discharge control for the
battery units in response to a situation of each of batteries which
the battery units individually have.
[0006] According to another embodiment of the present disclosure,
there is provided a control method including discriminating a
plurality of battery units which are to share and output electric
power required by a load, and carrying out discharge control for
the battery units in response to a situation of each of batteries
which the battery units individually have.
[0007] According to a further embodiment of the present disclosure,
there is provided a control system including a plurality of battery
units, and a control apparatus connected to the battery units, the
control apparatus including a discrimination section configured to
discriminate a plurality of battery units which are to share and
output electric power required by a load from among the battery
units, and a control section configured to carry out discharge
control for the battery units in response to a situation of each of
batteries which the battery units individually have.
[0008] At least with one of the embodiments, when discharge from a
plurality of battery units is carried out, the discharge amount can
be controlled for each battery unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a block diagram showing an example of a
configuration of a system;
[0010] FIG. 2 is a block diagram showing an example of a
configuration of a control unit;
[0011] FIG. 3 is a block diagram showing an example of a
configuration of a power supply system of the control unit;
[0012] FIG. 4 is a circuit diagram showing an example of a
particular configuration of a high voltage input power supply
circuit of the control unit;
[0013] FIG. 5 is a block diagram showing an example of a
configuration of a battery unit;
[0014] FIG. 6 is a block diagram showing an example of a
configuration of a power supply system of the battery unit;
[0015] FIG. 7 is a circuit diagram showing an example of a
particular configuration of a charger circuit of the battery
unit;
[0016] FIG. 8A is a graph illustrating a voltage-current
characteristic of a solar cell, and FIG. 8B is a graph,
particularly a P-V curve, representative of a relationship between
the terminal voltage of the solar cell and the generated electric
power of the solar cell in the case where a voltage-current
characteristic of the solar cell is represented by a certain
curve;
[0017] FIG. 9A is a graph illustrating a variation of an operating
point with respect to a change of a curve representative of a
voltage-current characteristic of a solar cell, and FIG. 9B is a
block diagram showing an example of a configuration of a control
system wherein cooperation control is carried oat by a control unit
and a plurality of battery units;
[0018] FIG. 10A is a graph illustrating a variation of an operating
point when cooperation control is carried out in the case where the
illumination intensity upon a solar cell decreases, and FIG. 10B is
a graph illustrating a variation of an operating point when
cooperation control is carried out in the case where the load as
viewed from the solar cell increases;
[0019] FIG. 11 is a graph illustrating a variation of an operating
point when cooperation control is carried out in the case where
both of the illumination intensity upon the solar cell and the load
as viewed from the solar cell vary;
[0020] FIGS. 12 and 13 are flow charts illustrating an example of a
process for discriminating battery units which share a discharge
process;
[0021] FIG. 14 is a flow chart illustrating an example of a process
of determining a charge amount of a battery unit; and
[0022] FIGS. 15A and 15B are timing charts illustrating an example
of a discharge period for each battery unit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] In the following, an embodiment of the present disclosure is
described with reference to the accompanying drawings. It is to be
noted that the description is given in the following order.
<1. Embodiment>
<2. Modifications>
[0024] It is to be noted that the embodiment and the modifications
described below are specific preferred examples of the present
disclosure, and the present disclosure is not limited to the
embodiment and the modifications.
1. Embodiment
Configuration of the System
[0025] FIG. 1 shows an example of a configuration of a control
system according to the present disclosure. The control system is
configured from one or a plurality of control units CU and one or a
plurality of battery units BU. The control system 1 shown as an
example in FIG. 1 includes one control unit CU, and three battery
units BUa, BUb and BUc. When there is no necessity to distinguish
the individual battery units, each battery unit is suitably
referred to as battery unit BU.
[0026] In the control system 1, it is possible to control the
battery units BU independently of each other. Further, the battery
units BU can be connected independently of each other in the
control system 1. For example, in a state in which the battery unit
BUa and the battery unit BUb are connected in the control system 1,
the battery unit BUc can be connected newly or additionally in the
control system 1. Or, in a state in which the battery units BUa to
BUc are connected in the control system 1, it is possible to remove
only the battery unit BUb from the control system 1.
[0027] The control unit CU and the battery units BU are
individually connected to each other by electric power lines. The
power lines include, for example, an electric power line L1 by
which electric power is supplied from the control unit CU to the
battery units BU and another electric power line L2 by which
electric power is supplied from the battery units BU to the control
unit CU. Thus, bidirectional communication is carried out through a
signal line SL between the control unit CU and the battery units
BU. The communication may be carried out in conformity with such
specifications as, for example, the SMBus (System Management Bus)
or the UART (Universal Asynchronous Receiver-Transmitter).
[0028] The signal line SL is configured from one or a plurality of
lines, and a line to be used is defined in accordance with an
object thereof. The signal line SL is used commonly, and the
battery units BU are connected to the signal line SL. Each battery
unit BU analyzes the header part of a control signal transmitted
thereto through the signal line SL to decide whether or not the
control signal is destined for the battery unit BU itself. By
suitably setting the level and so forth of the control signal, a
command to the battery unit BU can be transmitted. A response from
a battery unit BU to the control unit CU is transmitted also to the
other battery units BU. However, the other battery units BU do not
operate in response to the transmission of the response. It is so
be noted that, while it is assumed that, in the press at example,
transmission of electric power and communication are carried out by
means of wires, they may otherwise be carried out by radio.
[General Configuration of the Control Unit]
[0029] The control unit CU is configured from a high voltage input
power supply circuit 11 and a low voltage input power supply
circuit 12. The control unit CU has one or a plurality of first
devices. In the present example, the control unit CU has two first
devices, which individually correspond to the high voltage input
power supply circuit 11 and the low voltage input power supply
circuit 12. It is to be noted that, although the terms "high
voltage" and "low voltage" are used herein, the voltages to be
inputted to the high voltage input power supply circuit 11 and the
low voltage input power supply circuit 12 may be included in the
same input range. The input ranges of the voltages which can be
accepted by the high voltage input power supply circuit 11 and one
low voltage input power supply circuit 12 may overlap with each
other.
[0030] A voltage generated, by an electric power generation section
which generates electricity in response to the environment is
supplied to the high voltage input power supply circuit 11 and the
low voltage input power supply circuit 12. For example, the
electric power generation section is an apparatus which generates
electricity by the sunlight or wind power. Meanwhile, the electric
power generation section is not limited to that apparatus which
generates electricity in response the natural environment. For
example, the electric power generation section may be configured as
an apparatus which generates electricity by human power. Although
an electric generator whose power generation energy fluctuates in
response to the environment or the situation is assumed in this
manner, also that electric generator whose power generation energy
does not fluctuate is applicable. Therefore, as seen in FIG. 1,
also AC power can be inputted to the control system 1. It is to be
noted that voltages are supplied from the same electric power
generation section or different electric power generation sections
to the high voltage input power supply circuit 11 and the low
voltage input power supply circuit 12. The voltage or voltages
generated by the electric power generation section or sections are
an example of a first voltage or voltages.
[0031] To the high voltage input power supply circuit 11, for
example, a DC (Direct Current) voltage V10 of approximately 75 to
100 V (volts) generated by photovoltaic power generation is
supplied. Alternatively, an AC (Alternating Current) voltage of
approximately 100 to 250 V may be supplied to the high voltage
input power supply circuit 11. The high voltage input power supply
circuit 11 generates a second voltage in response to a fluctuation
of the voltage V10 supplied thereto by photovoltaic power
generation. For example, the voltage V10 is stepped down by the
high voltage input power supply circuit 11 to generate the second
voltage. The second voltage is a DC voltage, for example, within a
range of 45 to 48 V.
[0032] When the voltage V10 is 75 V, the high voltage input power
supply circuit 11 converts the voltage V10 into 45 V. However, when
the voltage V10 is 100 V, the high voltage input power supply
circuit 11 converts the voltage V10 into 48 V. In response to a
variation of the voltage V10 within the range from 75 to 100 V, the
high voltage input power supply circuit 11 generates the second
voltage such that the second voltage changes substantially linearly
within the range from 45 to 48 V. The high voltage input power
supply circuit 11 outputs the generated second voltage. It is to be
noted that the rate of change of the second voltage need nor
necessarily be linear, but a feedback circuit may be used such that
the output of the high voltage input power supply circuit 11 is
used as it is.
[0033] To the low voltage input power supply circuit 12, a DC
voltage V11 within a range of 10 to 40 V generated, for example, by
electric power generation by wind or electric power generation by
human power is supplied. The low voltage input power supply circuit
12 generates a second voltage in response to a fluctuation of the
voltage V11 similarly to the high voltage input power supply
circuit 11. The low voltage input power supply circuit 12 steps up
the voltage V11, for example, to a DC voltage within the range of
45 to 48 V in response to a change of the voltage V11 within the
range from 10 V to 40 V. The stepped up DC voltage is outputted
from the low voltage input power supply circuit 12.
[0034] Both or one of the output voltages of the high voltage input
power supply circuit 11 and the low voltage input power supply
circuit 12 is inputted to the battery units BU. In FIG. 1, the DC
voltage supplied to the battery units BU is denoted by V12. As
described hereinabove, the voltage V12 is, for example, a DC
voltage within the range from 45 to 48 V. All or some of the
battery units BU are charged by the voltage V12. It is to be noted
that a battery unit BU which is discharging is not charged.
[0035] A personal computer may be connectable to the control unit
CU. For example, a USB (Universal Serial Bus) cable is used to
connect the control unit CU and the personal computer to each
other. The control unit CU may be controlled using the personal
computer.
[General Configuration of the Battery Unit]
[0036] A general configuration of a battery unit which is an
example of a second apparatus is described. While description is
given below taking the battery unit BUa as an example, unless
otherwise specified, the battery unit BUb and the battery unit BUc
have the same configuration.
[0037] The battery unit BUa includes a charger or charging circuit
41a, a discharger or discharging circuit 42a and a battery Ba. Also
the other battery units BU include a charger or charging circuit, a
discharger or discharging circuit and a battery. In the following
description, when there is no necessity to distinguish each
battery, it is referred to suitably as battery B.
[0038] The charger circuit 41a converts the voltage V12 supplied
thereto from the control unit CU into a voltage applicable to the
battery Ba. The battery Ba is charged based on the voltage obtained
by the conversion. It is to be noted that the charger circuit 41a
changes the charge rate into the battery Ba in response to a
fluctuation of the voltage V12.
[0039] Electric power outputted from the battery Ba is supplied to
the discharger circuit 42a. From the battery Ba, for example, a DC
voltage within a range from substantially from 12 to 55 V is
outputted. The DC voltage supplied from the battery Ba is converted
into a DC voltage V13 by the discharger circuit 42a. The voltage
V13 is a DC voltage of, for example, 48 V. The voltage V13 is
outputted from the discharger circuit 42a to the control unit CU
through the electric power line L2. It is to be noted that the DC
voltage outputted from the battery Ba may otherwise be supplied
directly to an external apparatus without by way of the discharger
circuit 42a.
[0040] Each battery B may be a lithium-ion battery, an olivine-type
iron phosphate lithium-ion battery, a lead battery or the like. The
batteries B of the battery units BU may be those of different
battery types from each other. For example, the battery Ba of the
battery unit BUa and the battery Bb of the battery unit BUb are
configured from a lithium-ion battery and the battery Bc of the
battery unit BUc is configured from a lead, battery. The number and
the connection scheme of battery cells in the batteries B can be
changed suitably. A plurality of battery cells may be connected in
series or in parallel. Or series connections of a plurality of
battery cells may be connected in parallel.
[0041] When the battery units discharge, in the case where the load
is light, the highest one of the output voltages of the battery
units is supplied as the voltage V13 to the electric power line L2.
As the load becomes heavier, the outputs of the battery units are
combined, and the combined output is supplied to the electric power
line L2. The voltage V13 is supplied to the control unit CU through
the electric power line L2. The voltage V13 is outputted from an
output port of the control unit CU. To the control unit CU,
electric power can be supplied in a distributed relationship from
the battery units BU. Therefore, the burden on the individual
battery units BU can be moderated.
[0042] For example, the following use form may be available. The
voltage V13 outputted from, the battery unit BUa is supplied, to an
external apparatus through the control unit CU. To the battery unit
BUb, the voltage V12 is supplied from the control unit CU, and the
battery Bb of the battery unit BUb is charged. The battery unit BUc
is used as a redundant power supply. For example, when the
remaining capacity of the battery unit BUa drops, the battery unit
to be used is changed over from the battery unit BUa to the battery
unit. BUc and the voltage V13 outputted from the battery unit BUc
is supplied to the external apparatus. Naturally, the use form
described is an example, and the use form of the control system 1
is not limited to this specific use form.
[Internal Configuration of the Control Unit]
[0043] FIG. 2 shows an example of an internal configuration of the
control unit CU. As described hereinabove, the control unit CU
includes the high voltage input power supply circuit 11 and the low
voltage input power supply circuit 12. Referring to FIG. 2, the
high voltage input power supply circuit 11 includes an AC-DC
converter 11a for converting an AC input to a DC output, and a
DC-DC converter 11b for stepping down the voltage V10 to a DC
voltage within the range from 45 to 48 V. The AC-DC converter 11a
and the DC-DC converter 11b may be those of known types. It is to
be noted that, in the case where only a DC voltage is supplied to
the high voltage input power supply circuit 11, the AC-DC converter
11a may be omitted.
[0044] A voltage sensor, an electronic switch and a current sensor
are connected to each of an input stage and an output stage of the
DC-DC converter 11b. In FIG. 2 and also in FIG. 5 hereinafter
described, the voltage sensor is represented by a square mark; the
electronic switch by a round mark; and the current sensor by a
round, mark with slanting lines individually in a simplified
representation. In particular, a voltage sensor 11c, an electronic
switch 11d and a current sensor 11e are connected to the input
stage of the DC-DC converter 11b. A current sensor 11f, an
electronic switch 11g and a voltage sensor 11h are connected to the
output stage of the DC-DC converter 11b. Sensor information
obtained by the sensors is supplied to a CPU (Central Processing
Unit) 13 hereinafter described. On/off operations of the electronic
switches are controlled by the CPU 13.
[0045] The low voltage input power supply circuit 12 includes a
DC-DC converter 12a for stepping up the voltage V11 to a DC voltage
within, the range from 45 to 48 V. A voltage sensor, an electronic
switch and a current sensor are connected to each of an input stage
and an output stage of the low voltage input power supply circuit
12. In particular, a voltage sensor 12b, an electronic switch 12c
and a current sensor 12d are connected to the input stage of the
DC-DC converter 12a. A current sensor 12e, an electronic switch 12f
and a voltage sensor 12g are connected to the output stage of the
DC-DC converter 12a. Sensor information obtained by the sensors is
supplied to the CPU 13. On/off operations of the switches are
controlled by the CPU 13.
[0046] It is to be noted that, in FIG. 2, an arrow mark extending
from a sensor represents that sensor information is supplied to the
CPU 13. An arrow mark extending to an electronic switch represents
that the electronic switch is controlled by the CPU 13.
[0047] An output voltage of the high voltage input power supply
circuit 11 is outputted through a diode. An output voltage of the
low voltage input power supply circuit 12 is outputted through
another diode. The output voltage of the high voltage input power
supply circuit 11 and the output voltage of the low voltage input
power supply circuit 12 are combined, and the combined voltage V12
is outputted to the battery unit BU through the electric power line
L1. The voltage V13 supplied from the battery unit BU is supplied
to the control unit CU through the electric power line L2. Then,
the voltage V13 supplied to the control unit CU is supplied to the
external apparatus through an electric power line L3. It is to be
noted that, in FIG. 2, the voltage supplied to the external
apparatus is represented as voltage V14.
[0048] The electric power line L3 may be connected to the battery
units BU. By this configuration, for example, a voltage outputted
from the battery unit BUa is supplied to the control unit CU
through the electric power line L2. The supplied voltage is
supplied to the battery unit BUb through the electric power line L3
and can charge the battery unit BUb. It is to be noted that, though
not shown, power supplied to the control unit CU through the
electric power line L2 may be supplied to the electric power line
L1.
[0049] The control unit CU includes the CPU 13. The CPU 13 controls
the components of the control unit CU. For example the CPU 13
switches on/off the electronic switches of the high voltage input
power supply circuit 11 and the low voltage input power supply
circuit 12. Further, the CPU 13 supplies control signals to the
battery units BU. The CPU 13 supplies to the battery units BU a
control signal for turning on the power supply to the battery units
BU or a control signal for instructing the battery units BU to
charge or discharge. The CPU 13 can output control signals of
different contents to the individual battery units BU.
[0050] The CPU 13 is connected to a memory 15, a D/A (Digital to
Analog) conversion section 16, an A/D (Analog to Digital)
conversion section 17 and a temperature sensor 18 through a bus 14.
The bus 14 is configured, for example, from an I.sup.2C bus. The
memory 15 is configured from a nonvolatile memory such as an EEPROM
(Electrically Erasable and Programmable Read Only Memory). The D/A
conversion section 16 converts digital signals used in various
processes into analog signals.
[0051] The CPU 13 receives sensor information measured by the
voltage sensors and the current sensors. The sensor information is
inputted to the CPU 13 after it is converted into digital signals
by the A/D conversion section 17. The temperature sensor 18
measures an environmental temperature. For example, the temperature
sensor 18 measures a temperature in the inside of the control unit
CU or a temperature around the control unit CU.
[0052] The CPU 13 may have a communication function. For example,
the CPU 13 and a personal computer (PC) 19 may communicate with
each other. The CPU 13 may communicate not only with the personal
computer but also with an apparatus connected to a network such as
the Internet.
[Power Supply System of the Control Unit]
[0053] FIG. 3 principally shows an example of a configuration of
the control unit CU which relates to a power supply system. A diode
20 for the backflow prevention is connected to the output stage of
the high voltage input power supply circuit 11. Another diode 21
for the backflow prevention is connected to the output stage of the
low voltage input power supply circuit 12. The high voltage input
power supply circuit 11 and the low voltage input power supply
circuit 12 are connected to each other by OR connection by the
diode 20 and the diode 21. Outputs of the high voltage input power
supply circuit 11 and the low voltage input power supply circuit 12
are combined and supplied to the battery unit BU. Actually, that
one of the outputs of the high voltage input power supply circuit
11 and the low voltage input power supply circuit 12 which exhibits
a higher voltage is supplied to the battery unit BU. However, also
a situation in which the electric power from both of the high
voltage input power supply circuit 11 and the low voltage input
power supply circuit 12 is supplied is entered in response to the
power consumption of the battery unit BU which serves as a
load.
[0054] The control unit CU includes a main switch SW1 which can be
operated by a user. When the main switch SW1 is switched on,
electric power is supplied to the CPU 13 to start up the control
unit CU. The electric power is supplied to the CPU 13, for example,
from a battery 22 built in the control unit CU. The battery 22 is a
rechargeable battery such as a lithium-ion battery. A DC voltage
from the battery 22 is converted into a voltage, with which the CPU
13 operates, by a DC-DC converter 23. The voltage obtained by the
conversion is supplied as a power supply voltage to the CPU 13. In
this manner, upon start-up of the control unit CU, the battery 22
is used. The battery 22 is controlled, for example, by the CPU
13.
[0055] The battery 22 can be charged by electric power supplied
from the high voltage input power supply circuit 11 or the low
voltage input power supply circuit 12 or otherwise from the battery
units BU. Electric power supplied from the battery units BU is
supplied to a charger circuit 24. The charger circuit 24 includes a
DC-DC converter. The voltage V13 supplied from the battery units BU
is converted into a DC voltage of a predetermined level by the
charger circuit 24. The DC voltage obtained by the conversion is
supplied to the battery 22. The battery 22 is charged by the DC
voltage supplied thereto.
[0056] It is to be noted that the CPU 13 may operate with the
voltage V13 supplied thereto from the high voltage input power
supply circuit 11, low voltage input power supply circuit 12 or
battery units BU. The voltage V13 supplied from the battery units
BU is converted into a voltage of a predetermined level by a DC-DC
converter 25. The voltage obtained by the conversion is supplied as
a power supply voltage to the CPU 13 so that the CPU 13
operates.
[0057] After the control unit CU is started up, if at least one of
the voltages V10 and V11 is inputted, then the voltage V12 is
generated. The voltage V12 is supplied to the battery units BU
through the electric power line L1. At this time, the CPU 13 uses
the signal line SL to communicate with the battery units BU. By
this communication, the CPU 13 outputs a control signal for
instructing the battery units BU to start up and discharge. Then,
the CPU 13 switches on a switch SW2. The switch SW2 is configured,
for example, from an PET (Field Effect Transistor). Or the switch
SW2 may be configured from an IGBT (Insulated Gate Bipolar
Transistor). When the switch SW2 is on, the voltage V13 is supplied
from the battery units BU to the control unit CU.
[0058] A diode 26 for the backflow prevention is connected to the
output side of the switch SW2. The connection of the diode 26 can
prevent unstable electric power, which is supplied from a solar
battery or a wind power generation source, from being supplied
directly to the external apparatus. Thus, stabilised electric power
supplied from the battery units BU can be supplied to the external
apparatus. Naturally, a diode may be provided on the final stage of
the battery units BU in order to secure the safety.
[0059] In order to supply the electric power supplied from the
battery units BU to the external apparatus, the CPU 13 switches on
a switch SW3. When the switch SW3 is switched on, the voltage V14
based on the voltage V13 is supplied to the external apparatus
through the electric power line L3. It is to be noted that the
voltage V14 may be supplied to the other battery units BU so that
the batteries B of the other battery units BU are charged by the
voltage V14.
[0060] The CPU 13 has a function of acquiring the voltage of the
voltage V13 or the voltage V14. For example, a detection resistor
is connected to the electric power line L2 or the electric power
line L3 and the voltage across the detection resistor is measured
so that the CPU 13 acquires a voltage value of the voltage V13 or
the voltage V14. The CPU 13 monitors the voltage variation when a
predetermined battery unit and a predetermined load are connected
to the control unit CU.
[Example of the Configuration of the High Voltage Input Power
Supply Circuit]
[0061] FIG. 4 shows an example of a particular configuration of the
high voltage input power supply circuit. Referring to FIG. 14, the
high voltage input power supply circuit 11 includes the DC-DC
converter 11b and a feedforward controlling system hereinafter
described. In FIG. 4, the voltage sensor 11c, electronic switch
11d, current sensor 11e, current sensor 11f, electronic switch 11g
and voltage sensor 11h as well as the diode 20 and so forth are not
shown.
[0062] The low voltage input power supply circuit 12 is configured
substantially similarly to the high voltage input power supply
circuit 11 except that the DC-DC converter 12a is that of the
step-up type.
[0063] The DC-DC converter 11b is configured from a primary side
circuit 32 including, for example, a switching element, a
transformer 33, and a secondary side circuit 34 including a
rectification element and so forth. The DC-DC converter 11b shown
in FIG. 4 is that of the current resonance type, namely, an LLC
resonance converter.
[0064] The feedforward controlling system includes an operational
amplifier 35, a transistor 36 and resistors Rc1, Rc2 and Rc3. An
output of the feedforward controlling system is inputted to a
controlling terminal provided on a driver of the primary side
circuit 32 of the DC-DC converter 11b. The DC-DC converter 11b
adjusts the output voltage from the high voltage input power supply
circuit 11 so that the input voltage to the controlling terminal
may be fixed.
[0065] Since the high voltage input power supply circuit 11
includes the feedforward controlling system, the output voltage
from the high voltage input power supply circuit 11 is adjusted so
that the value thereof may become a voltage value within a range
set in advance. Accordingly, the control unit CU including the high
voltage input power supply circuit 11 has a function of a voltage
conversion apparatus which varies the output voltage, for example,
in response to a change of the input voltage from a solar cell or
the like.
[0066] As seen in FIG. 4, an output voltage is extracted from the
high voltage input power supply circuit 11 through the AC-DC
converter 11a including a capacitor 31, primary side circuit 32,
transformer 33 and secondary side circuit 34. The AC-DC converter
11a is a power factor correction circuit disposed where the input
to the control unit CU from the outside is an AC power supply.
[0067] The output from the control unit CU is sent to the battery
units BU through the electric power line L1. For example, the
individual battery units BUa, BUb and BUc are connected to output
terminals Te1, Te2, Te3, . . . through diodes D1, D2, D3, . . . for
the backflow prevention, respectively.
[0068] In the following, the feedforward controlling system
provided in the high voltage input power supply circuit 11 is
described.
[0069] A voltage obtained by stepping down the input voltage to the
high voltage input power supply circuit 11 to kc times, where kc is
approximately one several tenth or one hundredth, is inputted to
the non-negated input terminal of the operational amplifier 35.
Meanwhile, to the negated input terminal c1 of the operational
amplifier 35, a voltage obtained by stepping down a fixed voltage
Vt.sub.0 determined in advance to kc times is inputted. The input
voltage kc.times.Vt.sub.0 to the negated input terminal c1 of the
operational amplifier 35 is applied, for example, from the D/A
conversion section 16. The value of the voltage Vt.sub.0 is
retained in a built-in memory of the D/A conversion section 16 and
can be changed as occasion demands. The value of the voltage
Vt.sub.0 may otherwise be retained into the memory 15 connected to
the CPU 13 through the bus 14 such that if is transferred to the
D/A conversion section 16.
[0070] The output terminal of the operational amplifier 35 is
connected to the base of the transistor 36, and voltage-current
conversion is carried out in response to the difference between the
input voltage to the non-negated input terminal and the input
voltage to the negated input terminal of the operational amplifier
35 by the transistor 36.
[0071] The resistance value of the resistor Rc2 connected to the
emitter of the transistor 36 is higher than the resistance value of
the resistor Rc1 connected in parallel to the resistor Rc2.
[0072] It is assumed that, for example, the input voltage to the
high voltage input power supply circuit 11 is sufficiently higher
than the fixed voltage Vt.sub.0 determined in advance. At this
time, since the transistor 36 is in an on state, and the value of
the combined resistance of the resistor Rc1 and the resistor Rc2 is
lower than the resistance value of the resistor Rc1, the potential
at a point f shown in FIG. 4 approaches the ground potential.
[0073] Consequently, the input voltage to the controlling terminal
provided on the driver of the primary side circuit 32 and connected
to the point f through a photo-coupler 37 drops. The DC-DC
converter 11b which detects the drop of the input voltage to the
controlling terminal steps up the output voltage from the high
voltage input power supply circuit 11 so that the input voltage to
the controlling terminal may be fixed.
[0074] It is assumed now that, for example, the terminal voltage of
the solar cell connected to the control unit CU drops conversely
and the input voltage to the high voltage input power supply
circuit 11 approaches the fixed voltage Vt.sub.0 determined
advance.
[0075] As the input voltage to the high voltage input power supply
circuit 11 drops, the state of the transistor 36 approaches an off
state from an on state. As the state of the transistor 36
approaches an off state from an on state, current becomes less
likely to flow to the resistor Rc1 and the resistor Rc2, and the
potential at the point f shown in FIG. 4 rises.
[0076] Consequently, the input voltage to the controlling terminal
provided on the driver of the primary side circuit 32 is brought
out of a state in which it is kept fixed. Therefore, the DC-DC
converter 11b steps down the output voltage from the high voltage
input power supply circuit 11 so that the input voltage to the
controlling terminal may be fixed.
[0077] In other words, in the case where the input voltage is
sufficiently higher than the fixed voltage Vt.sub.0 determined
advance, the high voltage input power supply circuit 11 steps up
the output voltage. On the other hand, if the terminal voltage of
the solar cell drops and the input voltage approaches the fixed
voltage Vt.sub.0 determined in advance, then the high voltage input
power supply circuit 11 steps down the output voltage. In this
manner, the control unit CU including the high voltage input power
supply circuit 11 dynamically changes the output voltage in
response to the magnitude of the input voltage.
[0078] Furthermore, as hereinafter described, the high voltage
input power supply circuit 11 dynamically changes the output
voltage also in response to a change of the voltage required on the
output side of the control unit CU.
[0079] For example, it is assumed that the number of those battery
units BU which are electrically connected to the control unit CU
increases during electric generation of the solar cell. In other
words, it is assumed that the load as viewed from the solar cell
increases during electric generation of the solar cell.
[0080] In this instance, a battery unit BU is electrically
connected additionally to the control unit CU, and consequently,
the terminal voltage of the solar cell connected to the control
unit CU drops. Then, when the input voltage to the high voltage
input power supply circuit 11 drops, the state of the transistor 36
approaches an off state from an on state, and the output voltage
from the high voltage input power supply circuit 11 is stepped
down.
[0081] On the other hand, if it is assumed that the number of those
battery units BU which are electrically connected to the control
unit CU decreases during electric generation of the solar cell,
then the load as viewed from the solar cell decreases.
Consequently, the terminal voltage of the solar cell connected to
the control unit CU rises. If the input voltage to the high voltage
input power supply circuit 11 becomes sufficiently higher than the
fixed voltage Vt.sub.0 determined in advance, then the input
voltage to the controlling terminal provided on the driver of the
primary side circuit 32 drops. Consequently, the output voltage
from the high voltage input power supply circuit 11 is stepped
up.
[0082] It is to be noted that the resistance values of the
resistors Rc1, Rc2 and Rc3 are selected suitably such that the
value of the output voltage of the high voltage input power supply
circuit 11 may be included in a range set in advance. In other
words, the upper limit to the output voltage from the high voltage
input power supply circuit 11 is determined by the resistance
values of the resistors Rc1 and Rc2. The transistor 36 is disposed
so that, when the input voltage to the high voltage input power
supply circuit 11 is higher than the predetermined value, the value
of the output voltage from the high voltage input power supply
circuit 11 may not exceed the voltage value of the upper limit set
in advance.
[0083] On the other hand, the lower limit to the output voltage
from the high voltage input power supply circuit 11 is determined
by the input voltage to the non-negated input terminal of an
operational amplifier of a feedforward controlling system of the
charger circuit 41a as hereinafter described.
[Internal Configuration of the Battery Unit]
[0084] FIG. 5 shows an example of an internal configuration of the
battery units BU. Here, description is given taking the battery
unit BUa as an example. Unless otherwise specified, the battery
unit BUb and the battery unit BUc have a configuration similar to
that of the battery unit BUa.
[0085] Referring to FIG. 5, the battery unit BUa includes a charger
circuit 41a, a discharger circuit 42a and a battery Ba. The voltage
V12 is supplied from the control unit CU to the charger circuit
41a. The voltage V13 which is an output from the battery unit BUa
is supplied to the control unit CU through the discharger circuit
42a. The voltage V13 may otherwise be supplied directly to the
external apparatus from the discharger circuit 42a.
[0086] The charger circuit 41a includes a DC-DC converter 43a. The
voltage V12 inputted to the charger circuit 41a is converted into a
predetermined voltage by the DC-DC converter 43a. The predetermined
voltage obtained by the conversion is supplied to the battery Ba to
charge the battery Ba. The predetermined voltage differs depending
upon the type and so forth of the battery Ba. To the input stage of
the DC-DC converter 43a, a voltage sensor 43b, an electronic switch
43c and a current sensor 43d are connected. To the output stage of
the DC-DC converter 43a, a current sensor 43e, an electronic switch
43f and a voltage sensor 43g are connected.
[0087] The discharger circuit 42a includes a DC-DC converter 44a.
The DC voltage supplied from the battery Ba to the discharger
circuit 42a is converted into the voltage V13 by the DC-DC
converter 44a. The voltage V13 obtained by the conversion is
outputted from the discharger circuit 42a. To the input stage of
the DC-DC converter 44a, a voltage sensor 44b, an electronic switch
44c and a current sensor 44d are connected. To the output stage of
the DC-DC converter 44a, a current sensor 44e, an electronic switch
44f and a voltage sensor 44g are connected.
[0088] The battery unit BUa includes a CPU 45. The CPU 45 controls
the components of the battery unit BU. For example, the CPU 45
controls on/off operations of the electronic switches. The CPU 45
may carry out processes for assuring the safety of the battery B
such as an overcharge preventing function and an excessive current
preventing function. The CPU 45 is connected to a bus 46. The bus
46 may be, for example, an I.sup.2C bus.
[0089] To the bus 46, a memory 47, an A/D conversion section 48 and
a temperature sensor 49 are connected. The memory 47 is a
rewritable nonvolatile memory such as, for example, an EEPROM. The
A/D conversion section 48 converts analog sensor information
obtained by the voltage sensors and the current sensors into
digital information. The sensor information converted into digital
signals by the A/D conversion section 48 is supplied to the CPU 45.
The temperature sensor 49 measures the temperature at a
predetermined place in the battery unit BU. Particularly, the
temperature sensor 49 measures, for example, the temperature of the
periphery of a circuit board on which the CPU 45 is mounted, the
temperature of the charger circuit 41a and the discharger circuit
42a and the temperature of the battery Ba.
[Power Supply System of the Battery Unit]
[0090] FIG. 6 snows an example of a configuration of the battery
unit BUa principally relating to a power supply system. Referring
to FIG. 6, the battery unit BUa does not include a main switch. A
switch SW5 and a DC-DC converter 39 are connected between the
battery Ba and the CPU 45. Another switch SW6 is connected between
the battery Ba and the discharger circuit 42a. A further switch SW7
is connected to the input stage of the charger circuit 41a. A still
further switch SW8 is connected to the output stage of the
discharger circuit 42a. The switches SW are configured, for
example, from an FET.
[0091] The battery unit BUa is started up, for example, by a
control signal from the control unit CU. A control signal, for
example, of the high level is normally supplied from the control
unit CU to the battery unit BUa through a predetermined signal
line. Therefore, only by connecting a port of the battery unit BUa
to the predetermined signal line, the control signal, of the high
level is supplied to the switch SW5 making the switch SW5 in an on
state to start up the battery unit BUa. When the switch SW5 is on,
a DC voltage from the battery Ba is supplied to the DC-DC converter
39. A power supply voltage for operating the CPU 45 is generated by
the DC-DC converter 39. The generated power supply voltage is
supplied, to the CPU 45 to operate the CPU 45.
[0092] The CPU 45 executes control in accordance with an
instruction of the control unit CU. For example, a control signal
for the instruction to charge is supplied from the control unit CU
to the CPU 45. In response to the instruction to charge, the CPU 45
switches off the switch SW6 and the switch SW8 and then switches on
the switch SW7. When the switch SW7 is on, the voltage V12 supplied
from the control unit CU is supplied to the charger circuit 41a.
The voltage V12 is converted into a predetermined voltage by the
charger circuit 41a, and the battery Ba is charged by the
predetermined voltage obtained by the conversion. It is to be noted
that the charging method into the battery B can be changed suitably
in response to the type of the battery B.
[0093] For example, a control, signal for the instruction to
discharge is supplied from the control unit CU to the CPU 45. In
response to the instruction to discharge, the CPU 45 switches off
the switch SW7 and switches on the switches SW6 and SW8. For
example, the switch SW8 is switched on after a fixed interval of
time after the switch SW6 is switched on. When the switch SW6 is
on, the DC voltage from the battery Ba is supplied, to the
discharger circuit 42a. The DC voltage from the battery Ba is
converted into the voltage V13 by the discharger circuit 42a. The
voltage V13 obtained by the conversion is supplied to the control
unit CU through the switch SW8. It is to be noted that, though not
shown, a diode may be added to a succeeding stage to the switch SW8
in order to prevent the output of the switch SW8 from interfering
with the output from a different one of the battery units BU.
[0094] It is to be noted that, if an instruction of a timing for
charge or discharge is issued from the control unit CU to each
battery unit BU in advance, then the CPU 45 of the battery unit BU
can carry out a charge or discharge operation in accordance with
the designated timing.
[0095] It is to be noted that the discharger circuit 42a can be
changed over between on and off by control of the CPU 45. In this
instance, an ON/OFF signal line extending from the CPU 45 to the
discharger circuit 42a is used. For example, a switch SW not shown
is provided on the output side of the switch SW6. The switch SW in
this instance is hereinafter referred to as switch SW10 taking the
convenience in description into consideration. The switch SW10
carries out changeover between a first path which passes the
discharger circuit 42a and a second path which does not pass the
discharger circuit 42a.
[0096] In order to turn on the discharger circuit 42a, the CPU 45
connects the switch SW10 to the first path. Consequently, an output
from the switch SW6 is supplied to the switch SW8 through the
discharger circuit 42a. In order to turn off the discharger circuit
42a, the CPU 45 connects the switch SW10 to the second path.
Consequently, the output from the switch SW6 is supplied directly
to the switch SW8 without by way of the discharger circuit 42a.
[Example of the Configuration of the Charger Circuit]
[0097] FIG. 7 shows an example of a particular configuration of the
charger circuit of the battery unit. Referring to FIG. 1, the
charger circuit 41a includes a DC-DC converter 43a, and a
feedforward controlling system and a feedback controlling system
hereinafter described. It is to be noted that, in FIG. 7, the
voltage sensor 43b, electronic switch 43c, current sensor 43d,
current sensor 43e, electronic switch 43f, voltage sensor 43g,
switch SW7 and so forth are not shown.
[0098] Also the charger circuits of the battery units BU have a
configuration substantially similar to that of the charger circuit
41a shown in FIG. 7.
[0099] The DC-DC converter 43a is configured, for example, from a
transistor 51, a coil 52, a controlling IC (Integrated Circuit) 53
and so forth. The transistor 51 is controlled by the controlling IC
53.
[0100] The feedforward controlling system includes an operational
amplifier 55, a transistor 56, and resistors Rb1, Rb2 and Rb3
similarly to the high voltage input power supply circuit 11. An
output of the feedforward controlling system is inputted, for
example, to a controlling terminal provided on the controlling IC
53 of the DC-DC converter 43a. The controlling IC 53 in the DC-DC
converter 43a adjusts the output voltage from the charger circuit
41a so that the input voltage to the controlling terminal may be
fixed.
[0101] In other words, the feedforward controlling system provided
in the charger circuit 41a acts similarly to the feedforward,
controlling system provided in the high voltage input power supply
circuit 11.
[0102] Since the charger circuit 41a includes the feedforward
controlling system, the output voltage from the charger circuit 41a
is adjusted so that the value thereof may become a voltage value
within a range set in advance. Since the value of the output
voltage from the charger circuit is adjusted to a voltage value
within the range set in advance, the charging current to the
batteries B electrically connected to the control unit CU is
adjusted in response to a change of the input voltage from the high
voltage input power supply circuit 11. Accordingly, the battery
units BU which include the charger circuit have a function of a
charging apparatus which changes the charge rate to the batteries
B.
[0103] Since the charge rate to the batteries B electrically
connected to the control unit CU is changed, the value of the input
voltage to the charger circuits of the battery units BU, or in
other words, the value of the output voltage of the high voltage
input power supply circuit 11 or the low voltage input power supply
circuit 12, is adjusted so as to become a voltage value within the
range set in advance.
[0104] The input to the charger circuit 41a is an output, for
example, from the high voltage input power supply circuit 11 or the
low voltage input power supply circuit 12 of the control unit CU
described hereinabove. Accordingly, one of the output terminals
Te1, Te2, Te3, . . . shown in FIG. 4 and the input terminal of the
charger circuit 41a are connected to each other.
[0105] As seen in FIG. 7, an output voltage from the charger
circuit 41a is extracted through the DC-DC converter 43a, a current
sensor 54 and a filter 59. The battery Ba is connected to a
terminal Tb1 of the charger circuit 41a. In other words, the output
from the charger circuit 41a is used as an input to the battery
Ba.
[0106] As hereinafter described, the value of the output voltage
from each charger circuit is adjusted so as to become a voltage
value within the range set in advance in response to the type of
the battery connected to the charger circuit. The range of the
output voltage from each charger circuit is adjusted by suitably
selecting the resistance value of the resistors Rb1, Rb2 and
Rb3.
[0107] Since the range of the output voltage from each charger
circuit is determined individually in response to the type of the
battery connected to the charger circuit, the type of the batteries
B provided in the battery units BU is not limited specifically.
This is because the resistance values of the resistors Rb1, Rb2 and
Rb3 in the charger circuits may be suitably selected in response to
the type of the batteries B connected thereto.
[0108] It is to be noted that, while the configuration wherein the
output of the feedforward controlling system is inputted to the
controlling terminal of the controlling IC 53 is shown in RIG. 7,
the CPU 45 of the battery units BU may supply an input to the
controlling terminal of the controlling IC 53. For example, the CPU
45 of the battery unit BU may acquire information relating to the
input voltage to the battery unit BU from the CPU 13 of the control
unit CU through the signal line SL. The CPU 13 of the control unit
CU can acquire information relating to the input voltage to the
battery unit BU from a result of measurement of the voltage sensor
11h or the voltage sensor 12g.
[0109] In the following, the feedforward controlling system
provided in the charger circuit 41a is described.
[0110] The input to the non-negated input terminal of the
operational amplifier 55 is a voltage obtained by stepping down the
input voltage to the charger circuit 41a to kb times, where kb is
approximately one several tenth to one hundredth. Meanwhile, the
input to the negated input terminal b1 of the operational amplifier
55 is a voltage obtained by stepping down a voltage Vb, which is to
be set as a lower limit to the output voltage from the high voltage
input power supply circuit 11 or the low voltage input power supply
circuit 12, to kb times. The input voltage kb.times.Vb to the
negated input terminal b1 of the operational amplifier 55 is
applied, for example, from the CPU 45.
[0111] Accordingly, the feedforward controlling system provided in
the charger circuit 41a steps up the output voltage from the
charger circuit 41a when the input voltage to the charger circuit
41a is sufficiently higher than the fixed voltage Vb determined in
advance. Then, when the input voltage to the charger circuit 41a
approaches the fixed voltage Vb determined in advance, the
feedforward controlling system steps down the output voltage from
the charger circuit 41a.
[0112] The transistor 56 is disposed so that, when the input
voltage to the charger circuit 41a is higher than the predetermined
value, the value of the output voltage from the charger circuit 41a
may not exceed an upper limit set in advance similarly to the
transistor 36 described hereinabove with reference to FIG. 4. It is
to be noted that the range of the value of the output voltage from
the charger circuit 41a depends upon the combination of the
resistance values of the resistors Rb1, Rb2 and Rb3. Therefore, the
resistance values of the resistors Rb1, Rb2 and Rb3 are adjusted in
response to the type of the batteries B connected to the charger
circuits.
[0113] Further, the charger circuit 41a includes also the feedback
controlling system as described hereinabove. The feedback
controlling system is configured, for example, from a current
sensor 54, an operational amplifier 57, a transistor 58 and so
forth.
[0114] If the current amount supplied to the battery Ba exceeds a
prescribed value set in advance, then the output voltage from the
charger circuit 41a is stepped down by the feedback controlling
system, and the current amount supplied to the battery Ba is
limited. The degree of the limitation to the current amount to be
supplied to the battery Ba is determined in accordance with a rated
value of the battery B connected to each charger circuit.
[0115] If the output voltage from the charger circuit 41a is
stepped down by the feedforward controlling system or the feedback
controlling system, then the current amount to be supplied to the
battery Ba is limited. When the current amount supplied to the
battery Ba is limited, as a result, charging into the battery Ba
connected to the charger circuit 41a is decelerated.
[0116] Now, different controlling methods are described taking the
MPPT control and the control by the voltage tracking method as
examples before the cooperation control which may be executed in
the embodiment of the present disclosure is described.
[MPPT Control]
[0117] First, an outline of the MPPT control is described
below.
[0118] FIG. 8A is a graph illustrating a voltage-current
characteristic of a solar cell. In FIG. 8A, the axis of ordinate
represents the terminal current of the solar cell and the axis of
abscissa represents the terminal voltage of the solar cell.
Further, in FIG. 8A, Isc represents an output current value when
the terminals of the solar cell, are short-circuited while light is
irradiated, upon the solar cell, and Voc represents an output
voltage when the terminals of the solar cell are open while light
is irradiated upon the solar cell. The current Isc and the voltage
Voc are called short-circuit current and open-circuit voltage,
respectively.
[0119] As seen in FIG. 8A, when light is irradiated upon the solar
cell, the terminal current of the solar cell indicates a maximum
value when the terminals of the solar cell are short-circuited. At
this time, the terminal voltage of the solar cell is almost 0 V. On
the other hand, when light is irradiated upon the solar cell, the
terminal voltage of the solar cell exhibits a maximum value when
the terminals of the solar cell are open. At this time, the
terminal current of the solar cell is substantially 0 A.
[0120] It is assumed now that the graph indicative of a
voltage-current characteristic of the solar cell is represented by
a curve C1 shown in FIG. 8A. Here, if a load is connected to the
solar cell, then the voltage and current to be extracted from the
solar cell depend upon the power consumption required by the load
connected to the solar cell. A point on the curve C1 represented by
a set of the terminal voltage and the terminal current of the solar
cell at this time is called operating point of the solar cell. It
is to be noted that FIG. 8A schematically indicates the position of
the operating point but does not indicate the position of an actual
operating point. This similarly applies also to an operating point
appearing on any other figure of the present disclosure.
[0121] If the operating point is changed on the curve
representative of a voltage-current characteristic of the solar
cell, then a set of a terminal voltage Va and terminal current Ia
with which the product of the terminal voltage and the terminal
current, namely, the generated electric power, exhibits a maximum
value, is found. The point represented by the set of the terminal
voltage Va and the terminal current Ia with which the electric
power obtained by the solar cell exhibits a maximum value is called
optimum operating point of the solar cell.
[0122] When the graph indicative of a voltage-current
characteristic of the solar cell is represented by the carve C1
illustrated in FIG. 8A, the maximum electric power obtained from
the solar cell is determined by the product of the terminal voltage
Va and the terminal current Ia which provide the optimum operating
point. In other words, when the graph indicating a voltage-current
characteristic of the solar cell is represented by the curve C1
illustrated in FIG. 8A, the maximum electric power obtained from
the solar cell is represented by the area of a shadowed region in
FIG. 8A, namely by Va.times.Ia. It is to be noted that the amount
obtained by dividing Va.times.Ia by Voc.times.Isc is a fill
factor.
[0123] The optimum operating point varies depending upon the
electric power required by the load connected to the solar cell,
and the point P.sub.A representative of the operating point moves
on the curve C1 as the electric power required by the load
connected to the solar cell varies. When the electric power amount
required by the load is small, the current to be supplied to the
load may be lower than the terminal current at the optimum
operating point. Therefore, the value of the terminal voltage of
the solar cell at this time is higher than the voltage value at the
optimum operating point. On the other hand, when the electric power
amount required by the load is greater than the electric power
amount which can be supplied at the optimum operating point, the
electric power amount exceeds the electric power which can be
supplied at the illumination intensity at this point of time.
Therefore, it is considered that the terminal voltage of the solar
cell drops toward 0 V.
[0124] Curves C2 and C3 shown in FIG. 8A indicate, for example,
voltage-current characteristics of the solar cell when the
illumination intensity upon the solar cell varies. For example, the
curve C2 shown in FIG. 8A corresponds to the voltage-current
characteristic in the case where the illumination intensity upon
the solar cell increases, and the curve C3 shown in FIG. 8A
corresponds to the voltage-current characteristic in the case where
the illumination intensity upon the solar cell decreases.
[0125] For example, if the illumination intensity upon the solar
cell increases and the curve representative of the voltage-current
characteristic of the solar cell changes from the curve C1 to the
curve C2, then also the optimum operating point varies in response
to the increase of the illumination intensity upon the solar cell.
It is to be noted that the optimum operating point at this time
moves from a point on the curve C1 to another point on the curve
C2.
[0126] The MPPT control is nothing but to determine an optimum
operating point with respect to a variation of a curve
representative of a voltage-current characteristic of the solar
cell and control the terminal voltage or terminal current of the
solar cell so that electric power obtained from the solar cell may
be maximised.
[0127] FIG. 8B is a graph, namely, a P-V curve, representative of a
relationship between the terminal voltage of the solar cell and the
generated electric power of the solar cell in the case where a
voltage-current characteristic of the solar cell is represented by
a certain curve.
[0128] If it is assumed that the generated electric power of the
solar cell assumes a maximum value Pmax at the terminal voltage at
which the maximum operating point is provided as seen in FIG. 8B,
then the terminal voltage which provides the maximum operating
point can be determined by a method called mountain climbing
method. A series of steps described below is usually executed by a
CPU or the like of a power conditioner connected between the solar
cell and the power system.
[0129] For example, the initial value of the voltage inputted from
the solar cell is set to V.sub.0, and the generated electric power
P.sub.0 at this time is calculated first. Then, the voltage to be
inputted from the solar cell is incremented by .epsilon., which is
greater than 0, namely, .epsilon.>0, to determine the voltage
V.sub.1 as represented by V.sub.1=V.sub.0+.epsilon.. Then, the
generated electric power P.sub.1 when the voltage inputted from the
solar cell is V.sub.1 is calculated. Then, the generated electric
powers P.sub.0 and P.sub.1 are compared with each other, and if
P.sub.1>P.sub.0, then the voltage to be inputted from the solar
cell is incremented by .epsilon. as represented by
V.sub.2=V.sub.1+.epsilon.. Then, the generated electric power
P.sub.2 when the voltage inputted from the solar cell is V.sub.2 is
calculated. Then, the resulting generated electric power P.sub.2 is
compared with the formerly generated electric power P.sub.1. Then,
if P.sub.2>P.sub.1, then the voltage to be inputted from the
solar cell is incremented by .epsilon. as represented by
V.sub.3=V.sub.2+.epsilon.. Then, the generated electric power
P.sub.3 when the voltage inputted from the solar cell is V.sub.3 is
calculated.
[0130] Here, if P.sub.3<P.sub.2, then the terminal voltage which
provides the maximum operating point exists between the voltages
V.sub.2 and V.sub.3. By adjusting the magnitude of .epsilon. in
this manner, the terminal voltage which provides the maximum
operating point can be determined with an arbitrary degree of
accuracy. A bisection method algorithm may be applied to the
procedure described above. It is to be noted that, if the P-V curve
has two or more peaks in such a case that a shade appears locally
on the light irradiation face of the solar cell, then a simple
mountain climbing method cannot cope with this. Therefore, the
control program requires some scheme.
[0131] According to the MPPT control, since the terminal voltage
can be adjusted such that the load as viewed from the solar cell is
always in an optimum state, maximum electric power can be extracted
from the solar cell in different weather conditions. On the other
hand, analog/digital conversion (A/D conversion) is required for
calculation of the terminal voltage which provides the maximum
operating point and besides multiplication is included in the
calculation. Therefore, time is required for the control.
Consequently, the MPPT control cannot sometimes respond to a sudden
change of the illumination intensity upon the solar cell in such a
case that the sky suddenly becomes cloudy and the illumination
intensity upon the solar cell changes suddenly.
[Control by the Voltage Tracking Method]
[0132] Here, if the curves C1 to C3 shown in FIG. 8A are compared
with each other, then the change of the open voltage Voc with
respect to the change of the illumination intensity upon the solar
cell, which may be considered a change of a curve representative of
a voltage-current characteristic, is smaller than the change of the
short-circuit current Isc. Further, all solar cells indicate
voltage-current characteristics similar to each other, and it is
known that, in the case of a crystal silicon solar cell, the
terminal voltage which provides the maximum operating point is
found around approximately 80% of the open voltage. Accordingly, it
is estimated that, if a suitable voltage value is set as the
terminal voltage of the solar cell and the output current of a
converter is adjusted so that the terminal voltage of the solar
cell becomes equal to the set voltage value, then electric power
can be extracted efficiently from the solar cell. Such control by
current limitation as just described is called voltage tracking
method.
[0133] In the following, an outline of the control by the voltage
tracking method is described. It is assumed that, as a premise, a
switching element is disposed between the solar cell and the power
conditioner and a voltage measuring instrument is disposed between
the solar cell and the switching element. Also it is assumed that
the solar cell is in a state in which light is irradiated
thereon.
[0134] First, the switching element is switched off, and then when
predetermined time elapses, the terminal voltage of the solar cell
is measured by the voltage measuring instrument. The reason why the
lapse of the predetermined time is waited before measurement of the
terminal voltage of the solar cell after the switching off of the
switching element is that it is intended to wait that the terminal
voltage of the solar cell is stabilized. The terminal voltage at
this time is the open voltage Voc.
[0135] Then, the voltage value of, for example, 80% of the open
voltage Voc obtained by the measurement is calculated as a target
voltage value, and the target voltage value is temporarily retained
into a memory or the like. Then, the switching element is switched
on to start energization of the converter in the power conditioner.
At this time, the output current of the converter is adjusted so
that the terminal voltage of the solar cell becomes equal to the
target voltage value. The sequence of processes described above is
executed after every arbitrary interval of time.
[0136] The control by the voltage tracking method is high in loss
of the electric power obtained by the solar cell in comparison with
the MPPT control. However, since the control by the voltage
tracking method can be implemented by a simple circuit and is lower
in cost, the power conditioner including the converter can be
configured at a comparatively low cost.
[0137] FIG. 9A illustrates a change of the operating point with
respect to a change of a curve representative of a voltage-current
characteristic of the solar cell. In FIG. 9A, the axis of ordinate
represents the terminal current of the solar cell, and the axis of
abscissa represents the terminal voltage of the solar cell.
Further, a blank round mark in FIG. 9A represents the operating
point when the MPPT control is carried out, and a solid round mark
in FIG. 9A represents the operating point when control by the
voltage tracking method is carried out.
[0138] It is assumed now that the curve representative of a
voltage-current characteristic of the solar cell is a curve C5.
Then, if it is assumed that, when the illumination intensity upon
the solar cell changes, the curve representative of the
voltage-current characteristic of the solar cell successively
changes from the curve C5 to a curve C8. Also the operating points
according to the control methods change in response to the change
of the curve representative of the voltage-current characteristic
of the solar cell. It is to be noted that, since the change of the
open voltage Voc with respect to the change of the illumination
intensity upon the solar cell is small, in FIG. 9A, the target
voltage value when control by the voltage tracking method is
carried out is regarded as a substantially fixed value Vs.
[0139] As can be seen from FIG. 9A, when the curve representative
of the voltage-current characteristic of the solar cell is a curve
C6, the degree of the deviation between the operating point of the
MPPT control and the operating point of the control by the voltage
tracking method is low. Therefore, it is considered that, when the
curve representative of the voltage-current characteristic of the
solar cell is the curve C6, there is no significant difference in
generated electric power obtained by the solar cell between the two
different controls.
[0140] On the other hand, if the curve representative of the
voltage-current characteristic of the solar cell is the curve C8,
then the degree of the deviation between the operating point of the
MPPT control and the operating point of the control by the voltage
tracking method is high. For example, if the differences .DELTA.V6
and .DELTA.V8 between the terminal voltage when the MPPT control is
applied and the terminal voltage when the control by the voltage
tracking method is applied, respectively, are compared with each
other as seen in FIG. 9A, then .DELTA.V6<.DELTA.V8. Therefore,
when the curve representative of the voltage-current characteristic
of the solar cell is the curve C8, the difference between the
generated electric power obtained from the solar cell when the MPPT
control is applied and the generated electric power obtained from
the solar cell when the control by the voltage tracking method is
applied is great.
[Cooperation Control of the Control Unit and the Battery Unit]
[0141] Now, an outline of cooperation control of the control unit
and the battery unit is described. In the following description,
control by cooperation or interlocking of the control unit and the
battery unit is suitably referred to as cooperation control.
[0142] FIG. 9B shows an example of a configuration of a control
system wherein cooperation control by a control unit and a
plurality of battery units is carried out.
[0143] Referring to FIG. 9B, for example, one or a plurality of
battery units BU each including a set of a charger circuit and a
battery are connected to the control unit CU. The one or plural
battery units BU are connected in parallel to the electric power
line L1 as shown in FIG. 9B. It is to be noted that, while only one
control unit CU is shown in FIG. 9B, also in the case where the
control system includes a plurality of control units CU, one or a
plurality of control units CU are connected in parallel to the
electric power line L1.
[0144] Generally, if it is tried to use electric power obtained by
a solar cell to charge one battery, then the MPPT control or the
control by the voltage tracking method described above is executed
by a power conditioner interposed between the solar cell and the
battery. Although the one battery may be configured from a
plurality of batteries which operate in an integrated manner,
usually the batteries are those of the single type. In other words,
it is assumed that the MPPT control or the control by the voltage
tracking method described above is executed by a single power
conditioner connected between a solar cell and one battery.
Further, the number and configuration, which is a connection scheme
such as parallel connection or series connection, of batteries
which make a target of charging do not change but are fixed
generally during charging.
[0145] In the meantime, in the cooperation control, the control
unit CU and the plural battery units BUa, BUb, BUc, . . . carry out
autonomous control so that the output voltage of the control unit
CU and the voltage required by the battery units BU are balanced
well with each other. As described hereinabove, the batteries B
included in the battery units BUa, BUb, BUc, . . . may be of any
types. In other words, the control unit CU according to the present
disclosure can carry out cooperation control for a plurality of
types of batteries B.
[0146] Further, in the configuration example shown in FIG. 9B, the
individual battery units BU can be connected or disconnected
arbitrarily, and also the number of battery units BU connected to
the control unit CU is changeable during electric generation of the
solar cell. In the configuration example shown in FIG. 9B, the load
as viewed from the solar cell is variable during electric
generation of the solar cell. However, the cooperation control can
cope not only with a variation of the illumination intensity on the
solar cell but also with a variation of the load as viewed from the
solar cell during electric generation of the solar cell. This is
one of significant characteristics which are not achieved by
configurations in related arts.
[0147] It is possible to construct a control system which
dynamically changes the charge rate in response to the supplying
capacity from the control unit CU by connecting the control unit CU
and the battery units BU described above to each other. In the
following, an example of the cooperation control is described. It
is to be noted that, although, in the following description, a
control system wherein, in an initial state, one battery unit BUa
is connected to the control unit CU is taken as an example, the
cooperation control applies similarly also where a plurality of
battery units BU are connected to the control unit CU.
[0148] It is assumed that, for example, the solar cell is connected
to the input side of the control unit CU and the battery unit BUa
is connected to the output side of the control unit CU. Also it is
assumed that the upper limit to the output voltage of the solar
cell is 100 V and the lower limit to the output voltage of the
solar cell is desired to be suppressed to 75 V. In other words, it
is assumed that the voltage Vt.sub.0 is set to Vt.sub.0=75 V and
the input voltage to the negated input terminal of the operational
amplifier 35 is kc.times.75 V.
[0149] Further, it is assumed that the upper limit and the lower
limit to the output voltage from the control unit CU are set, for
example, to 48 V and 45 V, respectively. In other words, it is
assumed that the voltage Vb is set to Vb=45 V and the input voltage
to the negated input terminal of the operational amplifier 55 is
kb.times.45 V. It is to be noted that the value of 48 V which is
the upper limit to the output terminal from the control unit CU is
adjusted by suitably selecting the resistors Rc1 and Rc2 in the
high voltage input power supply circuit 11. In other words, it is
assumed that the target voltage value of the output from the
control unit CU is set to 48 V.
[0150] Further, it is assumed that the upper limit and the lower
limit to the output voltage from the charger circuit 41a of the
battery unit BUa are set, for example, to 42 V and 28 V,
respectively. Accordingly, the resistors Rb1, Rb2 and Rb3 in the
charger circuit 41a are selected so that the upper limit and the
lower limit to the output voltage from the charger circuit 41a may
become 42 V and 28 V, respectively.
[0151] It is to be noted that a state in which the input voltage to
the charger circuit 41a is the upper limit voltage corresponds to a
state in which the charge rate into the battery Ba is 100% whereas
another state in which the input voltage to the charger circuit 41a
is the lower limit voltage corresponds to a state in which the
charge rate is 0%. In particular, the state in which the input
voltage to the charger circuit 41a is 48 V corresponds to the state
in which, the charge rate into the battery Ba is 100%, and the
state in which the input voltage to the charger circuit 41a is 45 V
corresponds to the state in which the charge rate into the battery
Ba is 0%. In response to the variation within the range of the
input voltage from 45 to 48 V, the charge rate is set within the
range of 0 to 100%.
[0152] It is to be noted that charge rate control into the battery
may be carried out in parallel to and separately from the
cooperation control. In particular, since constant current charging
is carried out at an initial stage of charging, the output from the
charger circuit 41a is feedback-adjusted to adjust the charge
voltage so that the charge current may be kept lower than fixed
current. Then at a final stage, the charge voltage is kept equal to
or lower than a fixed voltage. The charge voltage adjusted here is
equal to or lower than the voltage adjusted by the cooperation
control described above. By the control, a charging process is
carried out within the electric power supplied from the control
unit CU.
[0153] First, a change of the operating point when the cooperation
control is carried out in the case where the illumination intensity
upon the solar cell changes is described.
[0154] FIG. 10A illustrates a change of the operating point when
the cooperation control is carried out in the case where the
illumination intensity upon the solar cell decreases. In FIG. 10A,
the axis of ordinate represents the terminal current of the solar
cell and the axis of abscissa represents the terminal voltage of
the solar cell. Further, a blank round mark in FIG. 10A represents
an operating point when the MPPT control is carried out, and a
shadowed round mark in FIG. 10A represents an operating point when
the cooperation control is carried out. Curves C5 to C8 shown in
FIG. 10A represent voltage-current characteristics of the solar
cell when the illumination intensity upon the solar cell
changes.
[0155] It is assumed now that the electric power required by the
battery Ba is 100 W (watt) and the voltage-current characteristic
of the solar cell is represented by the curve C5 which corresponds
to the most sunny weather state. Further, it is assumed that the
operating point of the solar cell at this time is represented, for
example, by a point a on the curve C5, and the electric power or
supply amount supplied from the solar cell to the battery Ba
through the high voltage input power supply circuit 11 and the
charger circuit 41a is higher than the electric power or demanded
amount required by the battery Ba.
[0156] When the electric power supplied from the solar cell, to the
battery Ba is higher than the electric power required by the
battery Ba, the output voltage from the control unit CU to the
battery unit BUa, namely the voltage V12, is 48 V of the upper
limit. In particular, since the input voltage to the battery unit
BUa is 48 V of the upper limit, the output voltage from the charger
circuit 41a of the battery unit BUa is 42 V of the upper limit, and
charge into the battery Ba is carried out at the charge rate of
100%. It is to be noted that surplus electric power is abandoned,
for example, as heat. It is to be noted that, although it has been
described that the charge into the battery is carried out at 100%,
the charge into the battery is not limited to 100% but can be
adjusted suitably in accordance with a characteristic of the
battery.
[0157] If the sky begins to become cloudy from this state, then the
curve representative of the voltage-current characteristic of the
solar cell changes from the curve C5 to the curve C6. As the sky
becomes cloudy, the terminal voltage of the solar cell gradually
drops, and also the output voltage from the control unit CU to the
battery unit BUa gradually drops. Accordingly, as the curve
representative of the voltage-current characteristic of the solar
cell changes from the curve C5 to the curve C6, the operating point
of the solar cell moves, for example, to a point b on the curve
C6.
[0158] If the sky becomes cloudier from this state, then the curve
representative of the voltage-current characteristic of the solar
cell changes from the curve C6 to the curve C7, and as the terminal
voltage of the solar cell gradually drops, also the output voltage
from the control unit CU to the battery unit BUa drops. When the
output voltage from the control unit CU to the battery unit BUa
drops by some degree, the control system cannot supply the electric
power of 100% to the battery Ba any more.
[0159] Here, if the terminal voltage of the solar cell approaches
Vt.sub.0=75 V of the lower limit from 100 V, then the high voltage
input power supply circuit 11 of the control unit CU begins to step
down the output voltage to the battery unit BUa from 48 V toward
Vb=45 V.
[0160] After the output voltage from the control unit CU to the
battery unit BUa begins to drop, the input voltage to the battery
unit BUa drops, and consequently, the charger circuit 41a of the
battery unit BUa begins to step down the output voltage to the
battery Ba. When the output voltage from the charger circuit 41a
drops, the charge current supplied to the battery Ba decreases, and
the charging into the battery Ba connected to the charger circuit
41a is decelerated. In other words, the charge rate into the
battery Ba drops.
[0161] As the charge rate to the battery Ba drops, the power
consumption decreases, and consequently, the load as viewed from
the solar cell decreases. Consequently, the terminal voltage of the
solar cell rises or recovers by the decreased amount of the load as
viewed from the solar cell.
[0162] As the terminal voltage of the solar cell rises, the degree
of the drop of the output voltage from the control unit CU to the
battery unit BUa decreases and the input voltage to the battery
unit BUa rises. As the input voltage to the battery unit BUa rises,
the charger circuit 41a of the battery unit BUa steps up the output
voltage from the charger circuit 41a to raise the charge rate into
the battery Ba.
[0163] As the charge rate into the battery Ba rises, the load as
viewed from the solar cell increases and the terminal voltage of
the solar cell drops by the increased amount of the load as viewed
from the solar cell. As the terminal voltage of the solar cell
drops, the high voltage input power supply circuit 11 of the
control unit CU steps down the output voltage to the battery unit
BUa.
[0164] Thereafter, the adjustment of the charge rate described
above is repeated automatically until the output voltage from the
control unit CU to the battery unit. BUa converges to a certain
value to establish a balance between the demand and the supply of
the electric power.
[0165] The cooperation control is different from the MPPT control
in that it is not controlled by software. Therefore, the
cooperation control does not require calculation of the terminal
voltage which provides a maximum operating point. Further, the
adjustment of the charge rate by the cooperation control does not
include calculation by a CPU. Therefore, the cooperation control is
low in power consumption in comparison with the MPPT control, and
also the charge rate adjustment described above is executed in such
a short period of time of approximately several nanoseconds to
several hundred nanoseconds.
[0166] Further, since the high voltage input power supply circuit
11 and the charger circuit 41a merely detect the magnitude of the
input voltage thereto and adjust the output voltage, analog/digital
conversion is not required and also communication between the
control unit CU and the battery unit BUa is not required.
Accordingly, the cooperation control does not require complicated
circuitry, and the circuit for implementing the cooperation control
is small in scale.
[0167] Here, it is assumed that, at the point a on the curve C5,
the control unit CU can supply the electric power of 100 W and the
output voltage from the control unit CU to the battery unit BUa
converges to a certain value. Further, it is assumed that the
operating point of the solar cell changes, for example, to the
point c on the curve C7. At this time, the electric power supplied
to the battery Ba becomes lower than 100 W. However, as seen in
FIG. 10A, depending upon selection of the value of the voltage
Vt.sub.0, electric power which is not inferior to that in the case
wherein the MPPT control is carried out can be supplied to the
battery Ba.
[0168] If the sky becomes further cloudy, then the curve
representative of the voltage-current characteristic of the solar
cell changes from the curve C7 to the curve C8, and the operating
point of the solar cell changes, for example, to a point d on the
curve C8.
[0169] As seen in FIG. 10A, since, under the cooperation control,
the balance between the demand and the supply of electric power is
adjusted, the terminal voltage of the solar cell does not become
lower than the voltage Vt.sub.0. In other words, under the
cooperation control, even if the illumination intensity on the
solar cell drops extremely, the terminal voltage of the solar cell
does not become lower than the voltage Vt.sub.0 at all.
[0170] If the illumination intensity on the solar cell drops
extremely, then the terminal voltage of the solar cell comes to
exhibit a value proximate to the voltage Vt.sub.0, and the amount
of current supplied to the battery Ba becomes very small.
Accordingly, when the illumination intensity on the solar cell
drops extremely, although time is required for charging of the
battery Ba, since the demand and the supply of electric power in
the control system are balanced well with each other, the control
system does not suffer from the system down.
[0171] Since the adjustment of the charge rate by the cooperation
control is executed in very short time as described above,
according to the cooperation control, even if the sky suddenly
begins to become cloudy and the illumination intensity on the solar
cell decreases suddenly, the system down of the control system can
be avoided.
[0172] Now, a change of the operating point when the cooperation
control is carried out in the case where the load as viewed from
the solar cell changes is described.
[0173] FIG. 10B illustrates a change of the operating point when
the cooperation control is carried out in the case where the load
as viewed from the solar cell increases. In FIG. 10B, the axis of
ordinate represents the terminal current of the solar cell and the
axis of abscissa represents the terminal voltage of the solar cell.
Further, a shadowed round mark in FIG. 10B represents an operating
point when the cooperation control is carried out.
[0174] It is assumed now that the illumination intensity on the
solar cell does not change and the voltage-current characteristic
of the solar cell is represented by a curve C0 shown in FIG.
10B.
[0175] Immediately after the control system is started up, it
estimates that the power consumption in the inside thereof is
almost zero, and therefore, the terminal voltage of the solar cell
may be considered substantially equal to the open voltage.
Accordingly, the operating point of the solar cell immediately
after the startup of the control system may be considered existing,
for example, at a point e on the curve C0. It is to be noted that
the output voltage from the control unit CU to the battery unit BUa
may be considered to be 48 V of the upper limit.
[0176] After supply of electric power to the battery Ba connected
to the battery unit BUa is started, the operating point of the
solar cell moves, for example, to a point g on the curve C0. It is
to be noted that, since, in the description of the present example,
the electric power required by the battery Ba is 100 W, the area of
a region S1 indicated by a shadow in FIG. 10B is equal to 100
W.
[0177] When the operating point of the solar cell is at the point g
on the curve C0, the control system is in a state in which the
electric power supplied from the solar cell to the battery Ba
through the high voltage input power supply circuit 11 and the
charger circuit 41a is higher than the electric power required by
the battery Ba. Accordingly, the terminal voltage of the solar
cell, the output voltage from the control unit CU and the voltage
supplied to the battery Ba when the operating point of the solar
cell is at the point g on the curve C0 are 100 V, 48 V and 42 V,
respectively.
[0178] Here, it is assumed that the battery unit BUb having a
configuration similar to that of the battery unit BUa is newly
connected to the control unit CU. If it is assumed that the battery
Bb connected to the battery unit BUb requires electric power of 100
W for the charge thereof similarly to the battery Ba connected to
the battery unit BUa, then the power consumption increases and the
load as viewed from the solar cell increases suddenly.
[0179] In order to supply totaling electric power of 200 W to the
two batteries, the totaling output current must be doubled, for
example, while the output voltage from the charger circuit 41a of
the battery unit BUa and the charger circuit 41b of the battery
unit BUb is maintained.
[0180] However, where the power generator is the solar cell, also
the terminal voltage of the solar cell drops together with increase
of output current from the charger circuits 41a and 41b. Therefore,
the totaling output current must be higher than twice in comparison
with that in the case when the operating point of the solar cell is
at the point g. Therefore, the operating point of the solar cell
must be, for example, at a point h on the curve C0 as shown in FIG.
10B, and the terminal voltage of the solar cell drops extremely. If
the terminal voltage of the solar cell drops extremely, then the
control system may suffer from system down.
[0181] In the cooperation control, if the terminal voltage of the
solar cell drops as a result of new or additional connection of the
battery unit BUb, then adjustment of the balance between the demand
and the supply of electric power in the control system is carried
out. In particular, the charge rate into the two batteries is
lowered automatically so that electric power supplied to the
battery Ba and the battery Bb may totally become, for example, 150
W.
[0182] In particular, if the terminal voltage of the solar cell
drops as a result of new connection of the battery unit BUb, then
also the output voltage from the control unit CU to the battery
units BUa and BUb drops. If the terminal voltage of the solar cell
approaches Vt.sub.0=75 V of the lower limit from 100 V, then the
high voltage input power supply circuit 11 of the control unit CU
begins to step down the output voltage to the battery units BUa and
BUb toward Vb=45 V from 48 V.
[0183] As the output voltage from the control unit CU to the
battery units BUa and BUb is stepped down, the input voltage to the
battery units BUa and BUb drops. Consequently, the charger circuit
41a of the battery unit BUa and the charger circuit 41b of the
battery unit BUb begin to step down the output voltage to the
batteries Ba and Bb, respectively. As the output voltage from the
charger circuit drops, the charging into the batteries connected to
the charger circuit is decelerated. In other words, the charge rate
to each battery is lowered.
[0184] As the charge rate into each battery is lowered, the power
consumption decrease as a whole, and consequently, the load as
viewed from the solar cell decreases and the terminal voltage of
the solar cell rises or recovers by an amount corresponding to the
decreasing amount of the load as viewed from the solar cell.
[0185] Thereafter, adjustment of the charge rate is carried out
until the output voltage from the control unit CU to the battery
units BUa and BUb converges to a certain value to establish a
balance between the demand and the supply of electric power in a
similar manner as in the case where the illumination intensity on
the solar cell decreases suddenly.
[0186] It is to be noted that it depends upon the situation to
which value the voltage value actually converges. Therefore,
although the value to which the voltage value actually converges is
not known clearly, since charging stops when the terminal voltage
of the solar cell becomes equal to Vt.sub.0=75 V of the lower
limit, it is estimated that the voltage value converges to a value
a little higher than the value of Vt.sub.0 of the lower limit.
Further, it is estimated that, since the individual battery units
are not controlled in an interlocking relationship with each other,
even if the individual battery units have the same configuration,
the charge rate differs among the individual battery units due to a
dispersion of used elements. However, there is no change in that
the battery units can generally be controlled by the cooperation
control.
[0187] Since the adjustment of the charge rate by the cooperation
control is executed in a very short period of time, if the battery
unit BUb is connected newly, then the operating point of the solar
cell changes from the point g to a point i on the curve C0. It is
to be noted that, while a point h is illustrated as an example of
the operating point of the solar cell on the curve C0 for the
convenience of description in FIG. 10B, under the cooperation
control, the operating point of the solar cell does not actually
change to the point h.
[0188] In this manner, in the cooperation control, the charger
circuit of the individual battery units BU detects the magnitude of
the input voltage thereto in response to an increase of the load as
viewed from the solar cell, and automatically suppresses the
current amount to be sucked thereby. According to the cooperation
control, even if the number of those battery units BU which are
connected to the control unit CU increases to suddenly increase the
load as viewed from the solar cell, otherwise possible system down
of the control system can be prevented.
[0189] Now, a change of the operating point when the cooperation
control is carried out in the case where both of the illumination
intensity on the solar cell and the load as viewed from the solar
cell vary is described.
[0190] FIG. 11 illustrates a change of the operating point when the
cooperation control is carried out in the case where both of the
illumination intensity on the solar cell and the load as viewed
from the solar cell vary. In FIG. 11, the axis of ordinate
represents the terminal current of the solar cell and the axis of
abscissa represents the terminal voltage of the solar cell. A
shadowed round mark in FIG. 11 represents an operating point when
the cooperation control is carried out. Curves C5 to C8 shown in
FIG. 11 indicate voltage-current characteristics of the solar cell
in the case where the illumination intensity upon the solar cell
varies.
[0191] First, it is assumed that the battery unit BUa which
includes the battery Ba which requires the electric power of 100 W
for the charging thereof is connected to the control unit CU. Also
it is assumed that the voltage-current characteristic of the solar
cell at this time is represented by a curve C7 and the operating
point of the solar cell is represented by a point p on the curve
C7.
[0192] It is assumed that the terminal voltage of the solar cell at
the point p considerably approaches the voltage Vt.sub.0 set in
advance as a lower limit to the output voltage of the solar cell.
That the terminal voltage of the solar cell considerably approaches
the voltage Vt.sub.0 signifies that, in the control system,
adjustment of the charge rate by the cooperation control is
executed and the charge rate is suppressed significantly. In
particular, in the state in which the operating point of the solar
cell is represented by the point p shown in FIG. 11, the electric
power supplied to the battery Ba through the charger circuit 41a is
considerably higher than the electric power supplied to the high
voltage input power supply circuit 11 from the solar cell.
Accordingly, in the state in which the operating point of the solar
cell is represented by the point p shown in FIG. 11, adjustment of
the charge rate is carried out by a great amount, and electric
power considerably lower than 100 W is supplied to the charger
circuit 41a which charges the battery Ba.
[0193] It is assumed that the illumination intensity upon the solar
cell thereafter increases and the curve representative of the
voltage-current characteristic of the solar cell changes from the
curve C7 to the curve C6. Further, it is assumed that the battery
unit BUb which has a configuration similar to that of the battery
unit BUa is newly connected to the control unit CU. At this time,
the operating point of the solar cell changes, for example, front
the point p on the curve C7 to a point q on the curve C6.
[0194] Since the two battery units are connected to the control
unit CU, the power consumption when the charger circuits 41a and
41b fully charge the batteries Ba and Bb is 200 W. However, when
the illumination intensity upon the solar cell is not sufficient,
the cooperation control is continued and the power consumption is
adjusted to a value lower than 200 W such as, for example, to 150
W.
[0195] It is assumed here that the sky thereafter clears up and the
curve representative of the voltage-current characteristic of the
solar cell changes from the curve C6 to the curve C5. At this time,
when the generated electric power of the solar cell increases
together with the increase of the illumination intensity upon the
solar cell, the output current from the solar cell increases.
[0196] If the illumination intensity upon the solar cell increases
sufficiently and the generated electric power of the solar cell
further increases, then the terminal voltage of the solar cell
becomes sufficiently higher than the voltage Vt.sub.0 at a certain
point. If the electric power supplied from the solar cell to the
two batteries through the high voltage input power supply circuit
11 and the charger circuits 41a and 41b comes to be higher than the
electric power required to charge the two batteries, then the
adjustment of the charge rate by the cooperation control is
moderated or automatically cancelled.
[0197] At this time, the operating point of the solar cell is
represented, for example, by a point r on the curve C5 and charging
into the individual batteries Ba and Bb is carried out at the
charge rate of 100%.
[0198] Then, it is assumed that the illumination intensity upon the
solar cell decreases and the curve representative of the
voltage-current characteristic of the solar cell changes from the
curve C5 to the curve C6.
[0199] When the terminal voltage of the solar cell drops and
approaches the voltage Vt.sub.0 set in advance, the adjustment of
the charge rate by the cooperation control is executed again. The
operating point of the solar cell at this point of time is
represented by a point q of the curve C6.
[0200] It is assumed that the illumination intensity on the solar
cell thereafter decreases further and the curve representative of
the voltage-current characteristic of the solar cell changes from
the curve C6 to the curve C8.
[0201] Consequently, since the charge rate is adjusted so that the
operating point of the solar cell may not become lower than the
voltage Vt.sub.0, the terminal current from the solar cell
decreases, and the operating point of the solar cell changes from
the point q on the curve C6 to a point s on the curve C8.
[0202] In the cooperation control, the balance between the demand
and the supply of electric power between the control unit CU and
the individual battery units BU is adjusted so that the input
voltage to the individual battery units BU may not become lower
than the voltage Vt.sub.0 determined in advance. Accordingly, with
the cooperation control, the charge rate into the individual
batteries B can be changed on the real time basis in response to
the supplying capacity of the input side as viewed from the
individual battery units BU. In this manner, the cooperation
control can cope not only with a variation of the illumination
intensity on the solar cell but also with a variation of the load
as viewed from the solar cell.
[0203] As described hereinabove, the present disclosure does not
require a commercial power supply. Accordingly, the present
disclosure is effective also in a district in which a power supply
apparatus or electrical power network is not maintained.
[Load Determination Process and Discharge Controlling Process]
[0204] Incidentally, it is assumed that a plurality of battery
units are connected in parallel and operate while the output
voltages of the batteries of the battery units are different from
each other. After the operation is started, usually that one of the
batteries which exhibits the highest output voltage comes to
discharge and only the specific battery is exhausted. Further, if
the battery of the output source is changed over, then the output
voltage varies. This variation of the output voltage makes noise to
the load or external apparatus which receives supply of the output
voltage and may possibly have a bad influence on the load. If the
output voltage after the changeover is low and the power
consumption of the load is high, then the voltage will drop.
[0205] In order to cope with such a problem as just described,
cooperative processes may be carried out by and among the battery
units to adjust the output voltage. However, in such a case as
described as an example in the embodiment of the present disclosure
in which a battery can be newly connected or disconnected freely to
or from a system, it is actually difficult to carry out cooperative
processes among the battery units. Therefore, in the embodiment of
the present disclosure, a DC-DC converter is used to adjust the
output voltage to a predetermined voltage, for example, to 48 V, as
described hereinabove.
[0206] Also in the case where a DC-DC converter is used, the output
voltages of the battery units sometimes are not equal to each
other. For example, such a situation may possibly occur that, when
the output voltage of a specific battery unit is higher only by
approximately 0.01 V than the output voltages of the other battery
units, only the specific battery unit discharges. Naturally, the
difference in output voltage may possibly be absorbed in a process
of supplying electric power to the load, resulting in normal
operation of the battery units. However, in any case, it is very
difficult to grasp to which degree each battery discharges and
control the discharge amount.
[0207] In the system given as an example in the embodiment of the
present disclosure, a plurality of battery units are used. The
situation of batteries differs among the battery units. For
example, the batteries are different from each other in use
history, temperature, remaining capacity and so forth. Therefore,
it is sometimes demanded to set the discharge amount of a battery
of a certain battery unit to a high level because the battery is
new or to set the discharge amount of a battery of another battery
unit to a low level because the batteries suffer from
deterioration. However, since it is very difficult to control the
discharge amount for each battery, there is a problem that such a
demand as just described cannot be satisfied. Further, since the
power consumption of the load is not known, it cannot be determined
whether all battery units should be used or only some of the
battery units may be used from a relationship to the load.
[0208] Therefore, in the embodiment of the present disclosure, for
example, a load determination process and a discharge controlling
process are carried out so that the demand described above can be
satisfied. In the following, the load determination process and the
discharge controlling process are described. It is to be noted that
the discharge amount is, for example, an electric power amount
discharged by a certain battery unit. The discharge amount may
otherwise be defined by a period for which a battery unit
discharges, namely, by a discharge period. Or the discharge amount
may be defined by a distribution rate for each battery unit.
[0209] FIG. 12 is a flow chart illustrating an example of the load
determination process. The load determination process is carried
out by the control unit CU.
[0210] After the processing is started, at step S1, a process of
acquiring a situation of the batteries is carried out by the
control unit CU. In particular, for example, the CPU 13 of the
control unit CU signals, to the CPU 45 of each battery unit BU, a
requesting signal for requesting for a situation of the battery B
which the battery unit BU has. The requesting signal is
transmitted, for example, through the common signal line SL. The
requesting signal may otherwise be transmitted with an identifier
of each battery unit BU described in the header thereof or may be
transmitted by broadcast transmission to all battery units BU
without the identifiers of the battery units BU described
therein.
[0211] In response to the requesting signal, the CPU 45 of each
battery unit BU signals a response signal indicative of a situation
of the battery B which the battery unit BU has to the control unit
CU. The situation of a battery is data indicative of the remaining
capacity of the battery, a use history of the battery such as a
number of times of charge-discharge operations and a total time
period of use, a temperature of the battery and so forth. The
response signal is supplied from each battery unit BU to the
control unit CU. The control unit CU can acquire the situations of
the battery Ba of the battery unit BUa, the battery Bb of the
battery unit BUb and the battery 3c of the battery unit BUc based
on the response signals. It is to be noted that, in order to avoid
collision of the response signals from the battery units BU, the
response signals are transmitted one by one after every
predetermined interval of time. Then, the processing advances to
step S2.
[0212] At step S2, ranking in accordance with the remaining
capacity of the battery B is carried out. For example, the battery
units BU are ranked into the first rank, second rank, third rand, .
. . in the descending order of the remaining capacity of a battery
B included therein. Here, it is assumed that the first rank is
applied to the battery unit BUa; the second rank is applied to the
battery unit BUb; and the third rank is applied to the battery unit
BUc. Then, the processing advances to step S3.
[0213] At steps S3 and S4, a correction process for correcting the
ranks determined at step S2 is carried out. In particular, at step
S3, a correction process based on the use histories of the
batteries is carried out. For example, it is assumed that the
difference between the remaining capacities of the battery Ba of
the battery unit BUa of the first rank and the battery Bb of the
battery unit BUb of the second rank remains within a predetermined
range and is small. In such a case as just described, if the use
history of the battery Ba is longer than that of the battery Bb,
then the first and second ranks are exchanged. Naturally, even if
the correction process is carried out, the ranks may not possibly
change.
[0214] At step S4, a correction process based on the temperature in
the battery units BU is carried out. In particular, a correction
process is carried out such that, for example, the battery unit BU
having a higher temperature may have a lower rank. The processes at
steps S2, S3 and S4 may not be executed. Alternatively, at least
some of the processes may be executed. Or, another correction
process may be additionally carried out based on a parameter which
defines a situation of the batteries. For example, a correction
process based on the dischargeable electric power amount may be
carried out. The correction process may be carried out such that a
battery unit having a battery which has a smaller dischargeable
electric power amount, or in other words, having a battery which
cannot supply discharge current very much, may have a lower rank.
Then, the processing advances to step S5.
[0215] At step S5, the battery unit BUb to which the first, rank is
applied is selected. Then, the processing advances to step S6, at
which a discharging instruction is issued from the control unit CU
to the battery unit BUb. Since the contents of the process of the
discharging instruction are described hereinabove, overlapping
description of them is omitted herein to avoid redundancy. It is to
be noted that it is assumed that, when the process at step S6 is
carried out, for example, a load is connected to an electric power
line L4 of the control unit CU and operates. At this time, by what
degree the electric power is required by the load, namely, the
power consumption of the load, is unknown. Then, the processing
advances to step S7.
[0216] At step S7, it is decided whether or not the electric power
required by the load can be supplied by the battery unit BUb. This
process is carried out, for example, by the CPU 13 of the control
unit CU monitoring the voltage variation of the voltage V13
supplied to the electric power line L2. Alternatively, the
variation of the voltage on the load side may be monitored. Here,
as an example of the voltage V13, a DC voltage of 43 V is supplied
from the battery unit BUb to the electric power line L2. If the
power consumption of the load is high, or in other words, if the
load is heavy, then the voltage V13 drops by a great amount. As
occasion demands, the voltage V13 disappears. For example, a
threshold value is provided such that, when the voltage V13 becomes
equal to or lower than the threshold value, it is decided that the
battery unit BUb cannot supply the electric power required by the
load. If the voltage V13 does not drop or the variation of the V13
remains within a predetermined range, then it is decided that the
battery unit BUb can supply the electric power required by the
load, and the discharge process of the battery unit BUb is stopped.
Then, the processing advances to step S8.
[0217] At step S8, it is decided whether or not the process at step
S7 has been carried out for all of the battery units BU. If the
process has not been carried out in this manner, then the
processing returns to step S5. At step S5, the second battery unit
BUa is selected. Then at steps S6 and S7, charging instruction to
the battery unit BUa and decision of whether or not the electric
power required by the load can be supplied are carried out. After
the decision, the discharge process of the battery unit BUa is
stopped, and the processing advances to step S8.
[0218] Then at step S8, it is decided whether or not the process at
step S7 has been carried out for all of the battery units BU. If
the process has not been carried out, then the processing returns
to step S5. At step S5, the third battery unit BUc is selected.
Then at steps S6 and S7, charging instruction to the battery unit
BUc and decision of whether or not the electric power required by
the load can be supplied are carried out. After the decision, the
discharge process of the battery unit BUc is stopped, and the
processing advances to step S8.
[0219] Then at step S8, it is decided whether or not the process at
step S7 has been carried out for all of the battery units BU. Since
the process at step S7 has been carried out for all of the battery
unit BUa, battery unit BUb and battery unit BUc, the processing
advances to step S9. At step S9, it is decided whether or not the
individual battery units BU can output the electric power required
by the load. It all of the battery units BU cannot supply the
electric power required by the load, then the processing advances
to a process A. It is to be noted that details of the process A are
hereinafter described. If at least one of the battery units BU can
supply the electric power required by the load, then the processing
is ended.
[0220] Here, it is assumed that it is decided by the decision at
step S7 that, for example, each of the battery unit BUa, battery
unit BUb and battery unit BUc can supply the electric power
required by the load. In other words, each of the battery unit BUa,
battery unit BUb and battery unit BUc is independently ready for
the load. However, since the situations of the batteries of the
battery unit BUa, battery unit BUb and battery unit BUc are
different from one another, in the discharge controlling process
hereinafter described, a discharge process is carried out not by a
single one of the buttery units but is shared by the three battery
units.
[0221] It is to be noted that a battery unit with regard to which
it is decided by the process at step S7 that it cannot supply the
electric power required by the load is not used in the discharge
controlling process hereinafter described. For example, it is
assumed that it is decided by the process at step S7 that the
battery unit BUc cannot supply the electric power required by the
load. In this instance, in the discharge controlling process
hereinafter described, the battery unit BUc is not used, but the
two battery units, namely the battery unit BUa and the battery unit
BUb, share and output the electric power required by the load.
[0222] While, in the process described above, the decision process
at step S7 is carried out for all battery units, the process can be
changed, suitably in the following manner. For example, if the
current which flows through the electric power line L2 is
substantially fixed, then the outputs, namely, the powers, of the
battery units BU are substantially same as each other from a
relationship to the voltage. In such a case as just described, the
decision process at step S7 may be carried out not for all battery
units but only for one battery unit.
[0223] Also it is possible to modify the process in the following
manner. For example, the outputs of the battery units BU are
acquired at step S1. At this time, if the outputs of all battery
units are substantially equal to each other, then the process may
be carry out only for one of the battery units. Further, in order
to make the process efficient, the decision process at step S7 may
be carried out in order beginning with the battery unit which
exhibits the lowest output. If the battery unit which exhibits the
lowest output is ready for the load, then also all of the other
battery units are ready for the load, and the process at step S7
can be omitted partly. In the case where the process at step S7 is
carried out for all battery units, the processes at steps S1 to S3
may be omitted.
[0224] A process when the load determination process advances to
the process A is described with reference to a flow chart of FIG.
13. That the process A is carried out signifies that, from such a
reason that the load is heavy or from a like reason, a single one
of the battery units connected to the load is not ready for the
load. Therefore, a plurality of battery units BU are used so as to
be ready for the load. At step S11, a plurality of, for example,
two, battery units BU are selected. Then, the processing advances
to step S12. At step S12, a discharging instruction is issued to
two battery units BU, and consequently, the two battery units BU
carry out a discharging process. Then, the processing advances to
step S13. At step S13, it is decided whether or not the electric
power required by the load can be supplied when the two battery
units BU are used. Then, the processing advances to step S14.
[0225] At step S14, it is decided whether or not all combinations
have been checked. Here, since the three battery units, namely, the
battery unit BUa, battery unit BUb and battery unit BUc, are used,
three combinations are available. If the process at step S13 has
not been carried out for all of the combinations, then the
processing returns to step S11. Then at step S11, two battery units
BU are selected so as to make a different combination. If the
process at step S13 has been carried out for all combinations, then
the processing advances to step S15.
[0226] If the electric power required by the load cannot be
supplied by any combination at step S15, then the process A is
carried out again. In other words, the three battery units BU are
used to carry out a discharge process. If the electric power
required by the load cannot be supplied even if the three battery
units BU are used, the electric power required by the load cannot
be supplied even if all battery units BU are used. In such a case
as just described, for example, an error indication is provided or
an alarming sound is generated. If it is decided at step S15 that a
sufficient supply amount can be assured by at least one of the
combinations of the battery units, then the processing is
ended.
[0227] Even if a load whose power consumption is unknown is newly
connected, it can be decided by the process described above by what
number of battery units BU should be used for discharge in order to
supply the electric power required by the load. Such a complicated
process as to decide the power consumption of the load strictly is
not required.
[0228] Now, the discharge controlling process carried out by the
control unit CU is described. FIG. 14 is a flow chart illustrating
a flow of the discharge controlling process. Referring to FIG. 14,
after the discharge controlling process is started, a process at
step S21 is carried out first. At step S21, the control unit CU
acquires a situation of the batteries B of the battery units BU.
This process is substantially similar to the process at step S1 in
FIG. 12, and therefore, overlapping description of the same is
omitted herein to avoid redundancy. It is to be noted that the
situation for each battery B acquired by the process at step S1 of
FIG. 12 may be retained into the memory 15 of the control unit CU.
Then, the processing advances to step S22.
[0229] At step S22, the CPU 13 of the control unit CU carries out a
process of determining the discharge amount for each of the battery
units BU connected to the control unit CU. The CPU 13 determines,
for example, a ratio by which the battery unit BUa, battery unit
BUb and battery unit BUc should discharge. The ratio is hereinafter
referred to suitably as discharge distribution ratio. In a simple
model, this ratio is determined to be 1/3. However, in the
embodiment of the present disclosure, the discharge distribution
ratio is determined in response to a situation of the batteries
B.
[0230] For example, the discharge distribution ratio is determined
such that a battery unit BU having a battery having a comparatively
great remaining capacity, a battery unit BU wherein the number of
times of charging into and discharging from a battery is
comparatively small, a battery unit BU of a comparative low
temperature or a battery unit BU having a comparatively great
dischargeable electric power amount outputs a comparatively great
discharge amount. Which one of those parameters which define a
situation of a battery B is used preferentially can be changed
suitably. The parameters may be weighted suitably. Or, the
parameters may be ranked for each battery unit BU as at step S2 of
FIG. 12 such that the discharge distribution ratio is determined
such that the rate at which a battery unit BU having a
comparatively high rank discharges may be comparatively high.
[0231] The discharge distribution ratio to the battery units is
determined in response to the situation of the batteries B. For
example, the discharge distribution ratio is determined such that,
with respect to the rate of 1 of the battery unit BUc, the rate of
the battery unit BUa is 2 and the rate of the battery unit BUb is
3. The discharge distribution ratio may be automatically
determined, for example, by the control unit CU or may be
determined by the user. Then, the processing advances to step
S23.
[0232] At step S23, the control unit CU signals an instruction
signal representative of a timing for discharge to each of the
battery units BU. In the header of the instruction signal, an ID
for each battery unit is described. In the part for the instruction
contents, namely, command data, of the instruction signal, a timing
at which discharge is to be started and a timing at which the
discharge is to be ended with reference to a timing at which a
synchronizing signal is received are defined. The instruction
signals are transmitted through the common signal line SL.
[0233] Each of the battery units BU takes in the instruction signal
transmitted on the signal line SL and analyzes the header of the
instruction signal to decide whether or not the instruction signal
is destined for the battery unit BU. If the taken-in instruction
signal is destined for the battery unit BU, then the battery unit
BU carries out discharge at the timing designated in the
instruction signal. The processes on the battery unit BU side
described above are carried out, for example, by the CPU 45. For
example, a RTC (Real Time Clock) is connected to the CPU 45 of each
battery unit BU such that the CPU 45 can determine a timing using
time information supplied thereto from the RTC. In this manner, a
timing for discharge is set in advance for each battery unit.
Consequently, the necessity to signal a controlling signal for
discharging instruction from the control unit CU to each battery
unit BU for each timing is eliminated, and the processing can be
carried out rapidly. Then, the processing advances to step S24.
[0234] At step S24, a synchronizing signal is transmitted from the
control unit CU to the battery units BU. The synchronizing signal
is transmitted by broadcast transmission to the battery unit BUa,
battery unit BUb and battery unit BUc, for example, through the
common signal line SL. Then, the processing advances to step S25.
At step S25, each battery unit BU starts discharge at a
predetermined timing in response to the synchronizing signal.
Naturally, the synchronizing signal may be transmitted through a
line different from the common signal line SL.
[0235] FIG. 15A illustrates an example of a discharge situation of
the battery units BU when the discharge process is shared by the
three battery units and an example of a discharge situation of the
battery units BU when the discharge process is shared by two
battery units. The output of each battery unit BU, namely, the
height in the graph, in FIG. 15A indicates the level of the
voltage. Since the output voltages of the battery units BU are set
so as to be equal to, for example, 48 V, the heights representative
of the levels of the voltage are substantially equal to each other.
FIG. 15B illustrates electric powers in the two cases. It is to be
noted that, while the discharge situations in the different cases
are shown continuously, there is no necessity to carry out the
processes continuously.
[0236] First, the example wherein the output of one battery unit is
shared by three battery units is described. In response to the
synchronizing signal sync supplied at timing t0, for example, the
battery unit BUa starts a discharge process. It has been verified
by the load determination process described hereinabove that the
electric power required by the load can be supplied by the output
of the single battery unit BUa.
[0237] Discharge from the battery Ba is carried out by the
discharge process, and a voltage is outputted from the battery unit
BUa. Since details of the discharge process by the battery unit BUa
are described hereinabove, overlapping description of the same is
omitted herein to avoid redundancy. The battery unit BUa stops the
discharge process at timing t1. The timings t0 and t1 are defined
by the instruction contents, namely, the command data, of the
instruction signal described hereinabove. The battery unit BUa
carries out the discharge process for a discharge period denoted by
t1a.
[0238] At timing t1, the battery unit BUb starts a discharge
process. It has been verified by the load determination process
described hereinabove that the electric power required by the load
can be supplied by the output of the single battery unit BUb.
Discharge from the battery Bb is carried out by the discharge
process, and a voltage is outputted from the battery unit BUb. The
battery unit BUb stops the discharge process at timing t2. The
timings t1 and t2 are defined in the instruction contents, namely,
in the command data, of the instruction signal described
hereinabove. The battery unit BUb carries out the discharge process
for a discharge period denoted by t1b.
[0239] The battery unit BUc starts a discharge process at timing
t2. It has been verified by the load determination process
described hereinabove that the electric power required by the load
can be supplied by the output of the single battery unit BUc.
Discharge from the battery Bc is carried out by the discharge
process, and a voltage is outputted from the battery unit BUc. The
battery unit BUc stops the discharge process at timing t3. The
timings t2 and t3 are defined in the instruction contents, namely,
in the command data, of the instruction signal described
hereinabove. The battery unit BUc carries out the discharge process
for a discharge period denoted by t1c.
[0240] The ratio of the discharge periods t1a, t1b and t1c is set
to approximately 2:3:1. By setting the discharge period suitably in
this manner, the discharge distribution ratio described above can
be implemented. At this time, the power supplied to the load
corresponds to the output of the substantially one battery unit as
seen in FIG. 15B. A next synchronizing signal is supplied from the
control unit CU at timing t3, and the discharge process by the
battery units BU described above is repeated.
[0241] Now, an example wherein the output of two battery units is
shared by three battery units is described. Here, it is assumed
that, in the process A of the load determination process described
hereinabove, it is decided that the electric power required by the
load can be supplied, for example, by the combination of the
battery unit BUa and the battery unit BUb or the combination of the
battery unit BUb and the battery unit BUc. It is to be noted that
the ranking and the discharge distribution ratio are set to same as
those in the case where the output is shared by three battery
units.
[0242] The battery unit BUa starts a discharge process in response
to a first synchronising signal at timing t10 as seen in FIG. 15A.
Then, the battery unit BUa ends the discharge process at timing
t1l. In particular, the battery unit BUa discharges for a period
from timing t10 to timing t11 as a discharge period t2a. The
battery unit. BUb starts a discharge process in response to the
first synchronizing signal at timing t10. This discharge process is
continued. Within a period from the synchronizing signal supplied
at timing t10 to a next synchronizing signal supplied at timing
t12, the battery unit BUb discharges for a period from timing t10
to timing t12 as a discharge period t2b. The battery unit BUc
starts a discharge process at timing t11. Then, the battery unit
BUc ends the discharge process at timing t12. In other words, the
battery unit BUc discharges for a period from timing t1l to timing
t12 as a discharge period t2c.
[0243] The discharge periods t2c and t2a are set substantially to
1:2. Consequently, the ratio among the discharge periods t2a, t2b
and t2c is set substantially to 2:3:1. Also in the case where
discharge is shared by a plurality of battery units in this manner,
the discharge distribution ratio can be determined in response to
the situations of the batteries, and a discharge process in
accordance with the discharge distribution ratio can be carried
out.
[0244] The electric power required by the load is shared by the
outputs of the two battery units BU. Therefore, the electric power
becomes substantially equal to twice as seen in FIG. 15B. It is to
be noted that, even when the electric power does not become
substantially equal to twice, no problem occurs because it has been
verified by the load determination process described hereinabove
with reference to FIG. 14 that the electric power required by the
load can be supplied.
[0245] In this manner, the output to the load can be shared by a
plurality of battery units. Further, discharge control for the
battery units can be carried out in response to a situation of the
batteries which the battery units have.
[0246] It is to be noted that, when a battery unit to be used for
discharge changes over, there is the possibility that the output
may instantaneously decrease to 0 or drop significantly due to a
delay in processing or the like. Therefore, discharge periods are
preferably set so as to partly overlap with each other. The
discharge periods are set such that, in FIGS. 15A and 15B, the
discharge periods t1a and t1b overlap with each other, for example,
at timing t1.
[0247] The process for setting discharge periods so as to overlap
with each other is carried out, for example, by the CPU 13. The CPU
13 sets the timing at which the battery unit BUa is to stop its
discharge process to a timing a little later in time than timing t1
and sets the timing at which the battery unit BUb is to start its
discharge process to a timing a little earlier in time than timing
t1. It is to be noted that the CPUs 45 of the battery units BU may
carry out such control that they start a discharge process a little
earlier than a designated discharge starting timing and stop the
discharge process a little later than a designated discharge ending
timing.
[0248] It is to be noted that, also when the output of one battery
unit is ready for the load, if the output of one battery unit does
not have a sufficient margin with respect to the power consumption
of the load, then two battery units may share the output for the
load. Further, for example, when a predetermined battery unit is
disconnected or when the electric power required by the load
varies, the discharge distribution ratio among the battery units
may be changed dynamically.
[0249] As described above, even when the power consumption and so
forth of the load are unknown, a battery unit or units which share
and output the electric power required by the load can be
determined. Among the determined battery units, the discharge
period and so forth can be changed in response to a situation of
batteries which the battery units have. Consequently, it is
possible to cope, for example, with a case in which it is desired
to use a certain battery unit frequently or suppress use of a
certain battery unit to the least frequency.
2. Modifications
[0250] Although the embodiment of the present disclosure has been
described, the present disclosure is not limited to the embodiment
described above but can be modified in various forms. All of the
configurations, numerical values, materials and so forth in the
present embodiment are mere examples, and the present disclosure is
not limited to the configurations and so forth given as the
examples. The configurations and so forth given as the examples can
be suitably changed within a range within which no technical
contradiction occurs.
[0251] For example, a variable resistor may be connected to the
output side of the DC-DC converter in each battery unit. The
resistance value of the variable resistor is suitably varied. If
the resistance value of the variable resistor is raised, then the
output voltage of, for example, 48 V from the DC-DC converter
drops. Consequently, the output voltage from the DC-DC converter or
converters which continue to output 48 V is supplied to an external
apparatus. In other words, control for allowing only a desired
battery unit or units to output a voltage by changing the
resistance value of the variable resistor can be implemented.
[0252] The control unit and the battery unit in the control system
may be portable. The control system described above may be applied,
for example, to an automobile or a house.
[0253] It is to be noted that the present disclosure may have such
configurations as described below.
(1)
[0254] A control apparatus, including:
[0255] a discrimination section configured to discriminate a
plurality of battery units which are to share and output electric
power required by a load; and
[0256] a control section configured to carry out discharge control
for the battery units in response to a situation of each of
batteries which the battery units individually have.
(2)
[0257] The control apparatus according to (1), wherein the control
section carries out the discharge control by determining a
discharge amount for each of the battery units.
(3)
[0258] The control apparatus according to (2), wherein the control
section determines a discharge amount for each of the battery units
by setting a discharge period with respect to a reference
signal.
(4)
[0259] The control apparatus according to (3), wherein a discharge
period for which a predetermined one of the battery units is to
carry out the discharge process and a discharge period for which
another one of the battery units is to carry out the discharge
process overlap with each other.
(5)
[0260] The control apparatus according to any one of (1) to (4),
wherein the situation of each of the batteries is at least one of a
remaining capacity of the battery, a use history of the battery and
a temperature of the battery.
(6)
[0261] The control apparatus according to any one of (1) to (5),
wherein the discrimination section successively connects the
battery units to the load and monitors a voltage supplied from the
connected one of the battery units to discriminate the battery
unit.
(7)
[0262] A control method, including:
[0263] discriminating a plurality of battery units which are to
share and output electric power required by a load; and
[0264] carrying out discharge control for the battery units in
response to a situation of each of batteries which the battery
units individually have.
(8)
[0265] A control system, including:
[0266] a plurality of battery units; and
[0267] a control apparatus connected to the battery units;
[0268] the control apparatus including [0269] a discrimination
section configured to discriminate a plurality of battery units
which are to share and output electric power required by a load
from among the battery units, and [0270] a control section
configured to carry out discharge control for the battery units in
response to a situation of each of batteries which the battery
units individually have.
[0271] The present disclosure contains subject matter related to
that disclosed in Japanese Priority Patent Application JP
2011-243964 filed in the Japan Patent Office on Nov. 7, 2011, the
entire content of which is hereby incorporated by reference.
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